Web services: Finding a receipt record using a PO number

Hello all,

I'm attempting to use X3 webservices to locate a matching receipt or receipts for a specific purchase order. I have created a web service for the PTH table, and in the data, I can see that the POHNUM is retrieved in one of the response segments, though I can't seem to query by that field. I also have created a web service for the PTD (receipt detail) table, but the data doesn't contain the same POHNUM field for some reason, and I can't seem to query by it there either.

For my workflow, I need to create an invoice for a PO that has a receipt, and I need to verify the invoice details against both the PO line and the receipt line to make sure that the proper quantity has been received.

Can anyone offer any assistance with this lookup?

Thank you,