Another BPM question

Yahoo Archive
1
We are on 8.03.409C and want to pass a Part.Checkbox12 entry to the PO and I have tried this Post-Processing Method-Directive 4gl code thru PO.GetNewPODetail.

find first ttPODetail where ttPODetail.rowmod = "U" or ttPODetail.rowmod = "A" no-lock no-error.
if available ttPODetail then do:
FIND FIRST TTPODetail WHERE TTPODetail.Partnum = Part.PartNum NO-LOCK No-error.
if available ttPODetail then do:
assign ttpodetail.CheckBox12 = Part.CheckBox12.
end.
end.

As I am faily inexperienced in BPM's it appears not to like the Part table logic and I would appreciate any input.