minimum time value under condition

Hi

I have a problem on my simulation
I have a time dependent simulation and I want to get the minimum time value when a phenomena occur ( The voltage V raise a value above a certain threshlod)

I want to get the time when the phenomena occur and I want it to be settle because I will use it in the simulation

I use a max and min function like this
max((V>threshlod)*min(t))
the minimum give the value when the phenomena occur and the max avoid that the final is equal to 0
But the max and min are function definied in domain and NOT GLOBALLY that means that max and min are looked in the model regarding the value computed before in the simulation

At the end I juste want the variable give me 0 before V<threshold and the minimal time value after V>threshold and this value has to stay constant

Thanks a lot
Guillaume