this is my form
the SEATS LEFT box is a display item with a fixed to total value of 217. When I enter a value in either of the three boxes which are Adult, Child, and Infant, the SEATS LEFT will subtract the total values of those three text items.
So I want it to stop when it reaches 0 (ZERO) and gives a message. I tried putting WHEN-VALIDATE AND POST_CHANGE triggers to the SEATS LEFT with this code, but nothing happens. It even goes down to a negative value.
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IF :SEATS_LEFT < 0 THEN
MESSAGE('NO SEATS AVAILABLE');
END IF
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