BDC to upload Non-editable fields

Hi Gurus

For a data migration exercise, Objective is to develop an LSMW / BDC to update 10 fields in a custom infotype.

Out of 10, only two fields are input fields and the rest of them are non-editable fields.

How do we write to a non-editable field???

If we cant do it through this, suggest a way out......

Thanks

Kumarpal Jain.