Using Process.Start in an expression shape

I am trying to start a process in an expression using the C# code:

System.Diagnostics.Process.Start("IExplore.exe");

For some reason this is not starting an instance of the browser when the 
orchestration is run. Can anybody shed some light on why this would be the

case?

I put in another line:

System.Console.Beep();

This code is definitely being hit, so I can't understand why the other
line 
is not being executed.

Thanks very much