creating wall climb with time limit

I'm trying to create a mechanic where the player can climb a wall for a short period of time before falling down. How would I create this mechanic? Can you please help me.

This is just one of many methods, and it might not be the best. But that's what spontanously came to mind:

wall climb timed.cap

Thanks for all the help Tulamide. I have one more question. How can I cause to the timer to reset if the player touches the ground or another wall? Thanks again for all your help.