Determine when function exceeds certain value in Simulink

I want to determine at what point function exceeds a certain value, and to use that moment as the time when I will call another function (because that other function is not active until that moment). For example I have a function sin(t), the function x^wshould be run at the moment when the function sin(5) exceeds the value 0.4, so I need to have number (time when fuction is higher than certain value) on output. How do I determine that moment, can I do that using for or while loop in block ,,MATLAB function''?