How to set up constraints to prevent updating Qty if shipment number has been assigned

Summary:

Hi Experts,

In one our business case, we need to prevent updating Qty and Request Date on OM lines.

The case is that shipment line has shipment header number or not.

If shipment header number has assigned, we need to prevent updating.

After stage lines,we can prevent using constraints.

However, I have no idea for the line which is shipment header number has assigned but not staged yet.

So let us know how to set up constraints.

If it's impossible, let us know how we can do by Extension.

FYI, we don't use a Pickwave so our shipment process is below.