Need to create Functional Module in XI

Hi All,

I have a requirement to create reconciliation for payment file which should include the total nos of line s ,Total Amount ,Debit amount,Credit amount.

I Got to know that we acan create this by using a functional module in XI.

Can anyone come across such type of requirement if yes then how can i create a functional module in XI..

Please let me how to create a f unctional module in XI...

Thanks,