passing internal table data from subroutine pool to internal table

Hi experts,

              i am working on sap standard scripts.here i need to populate additional fields into form layout.so for that i am writing code in external subroutine pool and calling that subroutine from my script as below.

PERFORM GET_DATA IN PROGRAM xxxxxx                                     USING &INPUTS&                                     CHANGING &OUTPUTS&                                     ENDPERFORM

Here what my requirement is ,i need to pass internal table data from subroutine pool to script.By using 'Changing' parameter i can only pass one variable  at a time.i tried writing write_form in subroutine pool .even though no use.please help me out.

Thanks and regards

Naresh bammidi