Use count down in codebehind

Question

i have a page in my website. i want to use count down in codebehind.
i have javascript code. but i also want it in code. i know maximum time and want to count it down.
pae is a test window a it is postedback again and again until questions ends. i want to use resume test option and i need remaining time of questions left.i need to use it in postback code behind. can any one help me?