Passing total PO Amount through BPM

I have a BPM to notify PO Approvers that a PO is awaiting approval. However, we have levels of authority, and I'd like to have the BPM determine which group of authorizers to send the email to by the PO amount. I can't, however, seem to find a field where the total PO amount is stored. A field query on the PO Entry or PO Tracker screen says "POHeader.DocTotOrder", and that field appears in a trace of the PO Business Object but it has a zero value, and there is no such field listed in the Data Dictionary. On the PO approval screen, the amount of the PO is listed as "APV.POAmount", which must be a temporary table. In order to get the PO amount, do I have to do the math of each line and misc charges?

Ernie Lowell
Diba Industries