How to work in a timer control in asp.net using c sharp?

Question

i need the result like this........

i have start and stop button in my form......

If i click the start  button......the timer has to start from 0:00:01

and if i click stop button at 0:05:46  ......then again if i ckick start button means

it will start from 0:05:47.......

pls reply....