Prorate EE Contribution amount for FSA plans

Hello Experts,

We have a requirement where we need to prorate the EE contribution amount for FSA plans.

So I enhanced function modules HR_BEN_ESS_GET_OVERVIEW_DATA and HR_BEN_ESS_PARTICIPATING_PLANS and that took care of the EE contribution amounts displayed on the plan screen, review screen and Save screen.

But I can't find a place where I can write logic to calculate the prorated amount for the pop up window that appears when a plan is selected.

Please see the attachment. I don't think there is any BADI / EXIT that triggers at this point.

Please help me figure out any FM that kicks in after the user hits 'Calculate' button on the pop up window.

Thanks.

Supriya