>Dear all
>i want to know how to change field format ( in detail band ) based on a variable value.
>for example i want if FldFmt = 1 so my field format be @J 999999.999 and if FldFmt = 2 so @J 999999.9
>Thanks for your help

Instead of defining the field as numeric, define it as character. In the expression enter something like this:

TransForm(MyData, IIF(FldFmt = 1, '@J 999999.999', IIF(FldFmt = 2, 'asldkfjalsdfj', 'alsdkfjas')