IsDefined("variable_name")

Evaluates a string value to determine if the variable named in the string value exists. IsDefined returns TRUE if the specified variable is found, FALSE if not found.

IsDefined provides an alternative to the ParameterExists function, eliminating the need for cumbersome expressions used to test for the existence of a variable:

Evaluate("ParameterExists(#var_name#)")

See also Evaluate.

variable_name

A string value, the name of the variable you want to test for. This value must always be enclosed in quotation marks.