To my knowledge that's not possible. Simulation time depends on:
- size of problem
- number of ports
- size of smallest mesh cell -> time step
- Q-factor of problem
As others have said you cannot calculate the time before you start the simulation since you are waiting for the energy to decay to -30/40 dB or whatever accuracy you have set.
After solving you can see how long it has taken from the results->view->logfile (migh be slightly different menu structure, I don't have CST in front of me)