Passing in a string to a thread I am about to start? [C# 2002]

[Shaitan00]

I am trying to accomplish something like this:

{
   string sType ="Update";
   Thread th1 = new Thread (new ThreadStart(Operation1(sType)));
   th1.Start();
}

private void Operaton1(string sType)
{
   if (sType == "Update")
   {
   }
   else
   {
   }
}

Obviouslly this doesn't work and returns and error message as follows:
Method name expected

It works fine if my "Operation1" has no parameters but I somehow need to pass the information from "sType" into the Thread itself...
How could I accomplish passing a STRING into a THREAD I am about to start?

Any help would be greatly appreciated.
Thanks,