plzLVERY IMPORTANT (Timer problem)

Question

hi i'm developing e-test system usinf asp.net and c# ,every thing is good,BUT the problem s that i need timer for the exam and did not affected with the refresh button whtch statrts the tmer from the begining if the student pressed on it. plz if you have the solution tell me t and give me instruction for applyng it because im new in ths field thanx alot Rami Jnena