SUM icon issue in ALV Report

HI all,

I have developed an ALV Report. In the ALV display, i would like to sum see the Sum (Total) of few fields like Qty, Net value etc when i select that particular column and click the 'SUM" icon.

In my Report when i do so, the Program is displaying Runtime Error.

How to resolve this issue?

Any idea?

Regards

Pavan