Expression: Text string that specifies the expression to evaluate. Prefix variable names with%. Use standard arithmetic and logical operators. You can also use a variety of mathematical and string functions, as well as numeric and string constants. Enclose string constants in double quotes.

Expression variable arguments: When the Expression field of the Edit Function dialog is activated (by pressing Enter or navigating to another field), the dialog displays a text field for each variable. For each field, enter a numeric value or text string. Values whose form is numeric are substituted into the expression as numbers; otherwise they are substituted into the expression as strings.