Solving drift-diffusion and current continuity simultaneously

Hallo comsol forum !!!

I am new to comsol and I would appreciate any of your help!

I am trying to solve this drift-diffusion equation d(nd)/dt = div(D*grad(nd) - v*nd) + G (G is the generation rate), where G,v,D are expressions of the electric field E, where E= d(V,y) and V is the voltage.

{ In the model I named Voltage as variable psi} .

V satisfies also the continuity equation: div(s*grad(V)) =0.

If I apply a voltage, the density nd changes and thus the function of the voltage changes too inside my domain, which influences the density nd again. My guess is that these two equations should be solved simultaneously and after the first simulation, every output of the continuity equation must be the initial value of V in order the fisrt equation to be solved again and so on!!! In addition, I suspect that the first equation requires a time-dependant solver(or step?) and the second equation a stationary solver(or step?).How do i do this? Does anyone have some piece of advice? :)

P.S In order to construct my equations I have used the coefficient form PDE for the first equation as Physics and the Poisson's equation for the second equation

Thank you very, very much !!!!