Invoice plan via BAPI_PO_CREATE1

Hi guys:

I need to create an invoice plan via BAPI_PO_CREATE1 but so far I can´t succeed doing this. Also, I tried to use BAPI_PO_GETDETAIL1 in order to get the  invoice plan data from a framework order but no data is showed.

The enter parameters of BAPI_PO_GETDETAIL1 are:

PURCHASEORDER: Here I enter my framework order

INVOICE PLAN: X (I assumed that activating this field, bapi will show the invoice plan data)

When I run this BAPI no invoice plan data is showed.

Can anybody help me?

Thanks in advance