Event based - change between two physics

Hi,

How is it possible to define for comsol to calculate the dependent variable for some specific time for one physics and some times for the other physics (defined PDE and fluid flow)?

Is it possible to use Event which is in the ODE interface?

My case study: My aim is to calculate the piezometric heads in specific locations in my domain, which piezometric head is changing during time. Therefore my model is time-dependent.
And I defined two physics (fluid flow: representing non-flooding condition and PDE: representing flooding condition).

Thanks in advance for your help.
Hope to hear your answers
Sepideh