Hello Nishant,
You can devise an algorithm to do this. For each clock.
For each rising edge detection, find the difference between the present time and the time of the previous rising edge and the frequency is the reciprocal of that difference.
If the frequency is within tolerance, set some status variable indicating OK, and set up a timer() function to return execute some time in the future, corresponding to your definition of "if during the simulation any of the clock dissapears or is stopped".
Do a similar thing when the timer() executes to make sure the clock frequency is still OK. You have to mess around with it a little to get it right, but I'm sure this is enough to get you going.
You get the idea, right?
You can also google around for "loss of clock detection".
Bob P.
www.RPeruzzi.com