I found the answer here:
http://www.yoda.arachsys.com/csharp/threads/timers.shtml

I wish I had found this before I posted (bg).
Tim

>If I use a System.Windows.Forms.Timer I can stop or start the timer with:

>

>System.Windows.Forms.Timer tmrCheckStuff = new System.Windows.Forms.Timer();
>this.tmrCheckStuff.Interval = 4000; // about 4 seconds
>this.tmrCheckStuff.Start;
>or
>this.tmrCheckStuff.Enabled = true;
>

>If I need to stop if for a moment while something else occurs, then restart it that is pretty easy. But if I use a Threading.Timer, how do I do this?
>I can issue a tmrCheckStuff.Change()
>

>AutoResetEvent autoEvent = new AutoResetEvent(false);
>TimerCallback timerDelegate = new TimerCallback(MyStuffClass.DoStuffMethod);
>private System.Threading.Timer tmrCheckStuff = new System.Threading.Timer(timerDelegate, autoEvent, 90000, 5000);
>
>I can change the time with:
>autoEvent.WaitOne(5000, false);
>tmrCheckStuff.Change(0, 9000);
>

>
>Is there a simple way to just start and stop this timer?
>Also, with the Callback how do I call a method in the same class as the timer is declared? the DoStuffMethod().
>Thanks
>Tim