OK, ok, so no X52.... hmmmmm
Well, first solution would be to buy a second throttle quadrant (that is what I did).
Second is, you can try something that Sokol wrote today:
You can assign the throttle to a combination of KEY+joystick axis(I have not tested it myself but was amazed to read about it):
So allocate:
CTRL+left thumb stick y-axis for your throttle. The moment you leave CTRL your y-axis is no longer active for throttle command.
To make maters easier I would allocate instead of CTRL a joystick button like the one on top of your left thumb.
As said I have no personal experience so thank okol if it worked.
And please post the results (it saves me the efford trying to test it myself)
Happy Flying
~S~