Thanks for your reply. I figgered this one out after trial and error. This is tested in the 747. My aim is to HOLD reverse thrust, so which ever key you use, it must remain in that position WHILE the thrust lever(s) are increased, so it is not possible to use the detent switch on the thrust lever for this as it cannot be in detent while also increasing thrust.
On my Saitek Throttle quadrant, I have 3 controls- thrust lever for all engines (black knob), feather lever (blue knob) and mixture leaver (red knob). Since the 747 does not use the red mixture lever, I programmed the detent on the mixture lever (red knob) as the Thrust HOLD switch, I then use the throttle lever (black knob) to increase thrust. So ultimately, depending on the detent of the mixture lever (red knob) the thrust lever would forward thrust or reverse thrust.
I saw a post somewhere where someone programmed the throttle lever detent switch as the Reverse Toggle, and thus to go into reverse thrust, you would first reduce throttles to zero, push the throttle lever into detent, then push the throttles full then when ready to stop reverse thrust, you would push the throttle to zero again, push the throttle into detent, then put it back to zero. Seems logical, but I was unable to keep track on whether the throttles were in forward or reverse in case I accidentally pushed the throttle into detent and I feel that would be catastrophic in mid flight.