How to stop an in-play horse race trigger firing after race has finished.

Hi everyone. "Execute trigger once per market" doesn't achieve what I need because if the trigger has not been executed during the actual race, it can then be fired when the race goes in-play again, due to there being a photo finish etc.
Is there a condition I can add to my trigger to stop it firing on any selection after the race has been run and initially suspended, before it can go back in-play again for any reason?
Advice from another wiser than I, would be very welcome. Thank you.

pjms

Something like that:
Trigger Expression last_inplay - event_off is less than mf_second

Hi Tim,
Thank you so much for your quick reply. I have added your suggested Trigger Expression at the end of the conditions for all my in-play triggers.
Many thanks.

pjms