Calculate a Ship Date AFTER Art Approval

We have clients requesting custom art on a project. We send the quote and require payment before we start the job and the system auto-calculates a ship date. If a client takes a long time to approve art, the ship date has to be manually changed. Sometimes they see that and sometimes they don't.

Would love to see a solution to click a button that says "ship date will be calculated after art approval". Once art is approved, the date would be calculated and a note ent to the client.