Custom Message During Outbound deliveries
I want to display a custom message during the delivery processing from sales order or from VL01n.
The message has to be displayed before the user saves the document.
Use a Static variable or may be a variable(As Global Static Variable in your implementation class) and check if the variable before calling the popup.
So set the variable after calling the popup for the first time and use that before calling the popup.
Hope it make sense.