Is it possible to unbind a function from a text UI at runtime?

Hi. I am sure there are better ways to do this. Basically the nodes below just get the game time and bind it to text so it looks like a stopwatch. At 90 seconds I want the game to end. So I would like to 1) call a custom event only once that fires to notify that 90 seconds has been reached and 2) There is no need for the function to continue to be called so I would ideally like to unbind it from the text UI but not sure that is possible.

Thanks

If you call SetText it overrides the binding, last time I tested it.