Suppress Epiocr Pop-UP and replace with our own

The following pop up occurs when you try and move more than the Job Completed into Inventory.

We want to make this an exception message vs. a warning. I have the BPM for the message, but now two messages pop up. What can I do to suppress the EPCOR Message. Granted the users should never be doing this so getting two messages isn’t the end of the world.