Report Properties Dialog Box, Variables
Select Variables on the Report Properties dialog box to add custom variables to your report. A variable is processed one time when you run the report and can be referenced throughout the report. Because the variable is calculated only one time, each reference to the variable will always use the same value.
Click to add an item to the list.
Click to delete the selected item from the list.
Type a case-sensitive name that begins with a letter and has no spaces. The name can include letters, numbers, or underscores (_).
Type a value for the variable or click the Expression (fx) button to write an expression.
To include a reference to a variable from an expression, use Visual Basic collection syntax. For example, the following expression specifies a report variable named LastUpdate: =Variables!LastUpdate.Value.