How to use the Mutex object

Hello,
I wonder how it is possible to use the Mutex object. I have created an example where Session_Start in Global.asax will call function dosomework()
But I only want the function to run if the Mutex object is free/released/not busy but I don't exactly now how to implement this. If the Mutex object is not free which would mean that the "dosomework()" is working, then we will not call "dosomework()"
void Session_Start(object sender, EventArgs e) { //Only start this thread if the Mutex object is FREE Thread thread = new Thread(dosomework); thread.Start(); } void dosomework() { //Do some work here }