Problem updating Unit Price on Sales Order with Line Loop

Hi Everyone, 

I've got a line loop that updates the Line Price on a Sales Order on Add/Update.

It updates the field correctly, however I then get a message...

There is a difference between the document total and its components. [Sales Order - Document Total]  [Message 439-138]

The total field is updated, but the SO then remains open/unsaved.

I think It might be a timing thing, so I added a popup message and even tried moving to a different field, but nothing is working.

Any ideas?