How to assign a variable to an offset in Customer Exit Variables?

Hi,

I have to display my plan amounts across periods. The periods to be displayed are dynamic based on the user entry variables for the start and end periods.

I have to display the plan amouts for the periods in between the start and end periods.

I am trying to use a cusomer exit variable to calculate the difference between the start and end periods and put it into a variable. But how can I assign a variable to the offset?

Please suggest, if something else should be done.

Regards,

Srini.