The datafield property of a textbox in Custom Reports can use VBScript Functions.  VBScript is a lightweigtht programming language based on Microsoft's Visual Basic.  It can be used to format or calculate values for the report.

The following are the VBScript Functions.

Date/Time Functions

CDate Converts a valid date and time expression to the variant of subtype Date
Date Returns the current system date
DateAdd Returns a date to which a specified time interval has been added.  DateAdd("d",4,Date) 
DateDiff Returns the number of intervals between two dates
DatePart Returns the specified part of a given date
DateSerial Returns the date for a specified year, month, and day.  DATESERIAL(Year,Month,Day) 
DateValue Returns a date.  DateValue(Date) 
Day Returns a number that represents the day of the month (between 1 and 31, inclusive)
FormatDateTime Returns an expression formatted as a date or time. FormatDateTime(Date,FormatNumber) 
Hour Returns a number that represents the hour of the day (between 0 and 23, inclusive)
IsDate Returns a Boolean value that indicates if the evaluated expression can be converted to a date
Minute Returns a number that represents the minute of the hour (between 0 and 59, inclusive)
Month Returns a number that represents the month of the year (between 1 and 12, inclusive)
MonthName Returns the name of a specified month
Now Returns the current system date and time
Second Returns a number that represents the second of the minute (between 0 and 59, inclusive)
Time Returns the current system time
Timer Returns the number of seconds since 12:00 AM
TimeSerial Returns the time for a specific hour, minute, and second
TimeValue Returns a time
Weekday Returns a number that represents the day of the week (between 1 and 7, inclusive)
WeekdayName Returns the weekday name of a specified day of the week
Year Returns a number that represents the year

Math Functions

Abs - Returns the absolute value of a specified number.  Abs(-1). 
Atn - Returns the arctangent of a specified number
Cos - Returns the cosine of a specified number (angle)
Exp - Returns e raised to a power
Hex - Returns the hexadecimal value of a specified number
Int - Returns the integer part of a specified number
Fix - Returns the integer part of a specified number
Log - Returns the natural logarithm of a specified number
Oct - Returns the octal value of a specified number
Rnd - Returns a random number less than 1 but greater or equal to 0
Sgn - Returns an integer that indicates the sign of a specified number
Sin - Returns the sine of a specified number (angle)
Sqr - Returns the square root of a specified number
Tan - Returns the tangent of a specified number (angle)

Conversion Functions

Asc Converts the first letter in a string to ANSI code
CBool Converts an expression to a variant of subtype Boolean
CByte Converts an expression to a variant of subtype Byte
CCur Converts an expression to a variant of subtype Currency
CDate Converts a valid date and time expression to the variant of subtype Date
CDbl Converts an expression to a variant of subtype Double
Chr Converts the specified ANSI code to a character
CInt Converts an expression to a variant of subtype Integer
CLng Converts an expression to a variant of subtype Long
CSng Converts an expression to a variant of subtype Single
CStr Converts an expression to a variant of subtype String
Hex Returns the hexadecimal value of a specified number
Oct Returns the octal value of a specified number

Format Functions

FormatCurrency Returns an expression formatted as a currency value
FormatDateTime Returns an expression formatted as a date or time
FormatNumber Returns an expression formatted as a number
FormatPercent Returns an expression formatted as a percentage

Array Functions

Array - Returns a variant containing an array
Filter - Returns a zero-based array that contains a subset of a string array based on a filter criteria
IsArray -  Returns a Boolean value that indicates whether a specified variable is an array
Join - Returns a string that consists of a number of substrings in an array
LBound - Returns the smallest subscript for the indicated dimension of an array
Split - Returns a zero-based, one-dimensional array that contains a specified number of substrings
UBound - Returns the largest subscript for the indicated dimension of an array

String Functions

InStr - Returns the position of the first occurrence of one string within another. The search begins at the first character of the string
InStrRev - Returns the position of the first occurrence of one string within another. The search begins at the last character of the string
LCase - Converts a specified string to lowercase
Left - Returns a specified number of characters from the left side of a string
Len - Returns the number of characters in a string
LTrim - Removes spaces on the left side of a string
RTrim - Removes spaces on the right side of a string
Trim - Removes spaces on both the left and the right side of a string
Mid - Returns a specified number of characters from a string
Replace - Replaces a specified part of a string with another string a specified number of times
Right - Returns a specified number of characters from the right side of a string
Space - Returns a string that consists of a specified number of spaces
StrComp - Compares two strings and returns a value that represents the result of the comparison
String - Returns a string that contains a repeating character of a specified length
StrReverse - Reverses a string
UCase - Converts a specified string to uppercase

Other Functions

CreateObject - Creates an object of a specified type
Eval - Evaluates an expression and returns the result
GetLocale Returns the current locale ID
GetObject Returns a reference to an automation object from a file
GetRef Allows you to connect a VBScript procedure to a DHTML event on your pages
InputBox Displays a dialog box, where the user can write some input and/or click on a button, and returns the contents
IsEmpty Returns a Boolean value that indicates whether a specified variable has been initialized or not
IsNull Returns a Boolean value that indicates whether a specified expression contains no valid data (Null)
IsNumeric Returns a Boolean value that indicates whether a specified expression can be evaluated as a number
IsObject Returns a Boolean value that indicates whether the specified expression is an automation object
LoadPicture Returns a picture object. Available only on 32-bit platforms
MsgBox Displays a message box, waits for the user to click a button, and returns a value that indicates which button the user clicked
RGB Returns a number that represents an RGB color value
Round Rounds a number
ScriptEngine Returns the scripting language in use
ScriptEngineBuildVersion Returns the build version number of the scripting engine in use
ScriptEngineMajorVersion Returns the major version number of the scripting engine in use
ScriptEngineMinorVersion Returns the minor version number of the scripting engine in use
SetLocale Sets the locale ID and returns the previous locale ID
TypeName Returns the subtype of a specified variable
VarType Returns a value that indicates the subtype of a specified variable

 

Custom (non-standard) functions

R.IIF Immediate If.  IIF([RECTYPE]=1,"Inactive","Active")
R.SQLRESULT Returns result of SQL statement.
R.STARTDATE - Returns the Start Date of the report
R.ENDDATE - Returns the End Date of the report