Custom Message At "SAVE" form on Sales Order Form

Hi Experts,

I've a requirement where we need to validate the PROMISE_DATE at Order Lines level. If there is any line in the form with promise date greater than a specific date , the warning message should pop up. However, the tricky part is user expectation is the validation message should pop up only once when the "SAVE" button (or ctrl+s) is pressed. It should not come for every line while user is entering the order. I added a personalization on Trigger Event "WHEN-VALIDATE-RECORD" trigger object "LINE" , but this validates each line as we keep on entering the lines. Hence the