Hi,
If I understood correctly,
you have data in a internal table and you need to transfer that into the table interfacing parameter in Function module
1. why don't you directly use the same table interfacing parameter instead of local internal table.
2. if its a big task and if you don't have time
try like this
Consider , Interface table parameter - IT_INTER & Local internal table LT_ITAB
IT_INTER[] = LT_ITAB[].
thanks
Sailkrishna