Thanks for reply
Api or code to create receiving transaction against po receipts.
You can determine the query/API yourself by referring to (How To Determine Table and Column Name from a Field in a Form in 11i (Doc ID 259722.1) -- Doc applies to R12 as well.
Or, you could enable trace and generate the TKPROF file and this will display the exact query used by the form -- FAQ: Common Tracing Techniques within the Oracle Applications 11i/R12 (Doc ID 296559.1)
Or, open the form using forms builder and get the query/code.