Timer that Stops and starts:

I want to start a timer when the game begins that counts up, but doesnt actually display the time during gameplay, but stops when a player has won and the screen goes to the player wins screen. From there i want that time to display in a text variable along with all the other statistics i have generated.

The timer will also need a reset function when starting up the game again.

How do i go about doing this???
Any help woudl be great!!!

Cheers
Peter.D