Your profile shows you are on Vista v8.03, and it’s been a LONG time since I was there, but here’s where to start.
CAVEAT… if any of the following terms sound like I’m speaking in a foreign language, then you really need to read the Business Process Management Education Document for Vista/Vantage 8.03. It’s not available on EpicWeb any more, but it is probably somewhere on your Epicor server.
First of all, turn on tracing and enter a Sales Order. As soon as you enter the Part Number on the order line and hit TAB, stop your trace and look in the trace document to find which Business Object fired when you did that (on Epicor 10.2.500, it’s SalesOrder.ChangePartNumMaster).
Next, create a Pre-Processing Method Directive BPM on that Business Object.
The Action you want to perform is going to be a query, and you’ll need to write the query to see if the part number just entered is found in the Part table… if not throw an error message.
I don’t remember the syntax of everything, but that should get you started.