Select Variables on the Series Group Properties dialog box to add custom variables to your report. A variable is processed when you first run the report and can be referenced throughout the report. Because the variable is calculated only once, each reference to the variable will always use the same value. This can be useful, for example, for capturing values that can change during run time, like a time stamp in a report header. Variable names must be unique throughout the report.
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.
Type an expression or click the Expression (fx) button to edit the expression. In the Expression pane, labeled Set expression for: Value, make sure that the expression begins with an equal (=) sign.