Has anybody been able to build a BAQ that pulls this information in PO Entry?

In tech details is shows no binding, but yet how does it retain the information?
Thanks!
Has anybody been able to build a BAQ that pulls this information in PO Entry?

In tech details is shows no binding, but yet how does it retain the information?
Thanks!
Comes from PODetail.CalcTranType which comes from PORel.TranType
I have a question,how to update the Trantype after PO saved,it seems to be disable for edit