You don't need to put anything in the on exit. When you define the report variable, check Count under Calculate and choose your group from the Reset dropdown.

>I have a report form. I defined a data grouping and variable nCount within my report.
>I want to count the number of group data printed in every page. I added the following expression on exit of group band:
> nCount + 1
>But the final value is 0. Why?