Include this script step: Exit Script[ Result: False ]
This step, with False returned as its value, terminates the event that triggered the script in the first place. It only works with triggers that "fire" before the triggering event completes--see Script Triggers in FileMaker Help for a list of those that are "pre-event".
PS. You might also consider using Else IF instead of two blocks of If -- End If in your script.
Thanks! I suspected it was an easy answer but I couldn't figure it out. And you are right, I should get used to the Else If blocks rather then the two If blocks. Have a great holiday!