I need hep with a timer !

I need to make a timer where in a menu i choose the option " Start " the function timer starts running and when the user chooses the option " Stop " the timer stops and shows the user the time that have passed. I'm using the choice = menu ( 'title' , 'option1' , ... ) menu, and i made something like Choice = menu ( ' Timer ', ' Start ' ) and when the user pressed start i wanted the timer to start running and another menu would appear with the ' stop ' option , and when the user pressed the stop button, Matlab would show the time that as passed