One straightforward way to achieve this is via the CMS scripting facility:
First create a map including the CMS controls.
copy this into your script editor:
%define throttle js1.a3
%define forward cms.b1
%define backward cms.b2
%define dead 40
if ( [throttle + dead < 128 ] ) then
forward = true;
backward = false;
else if ( [ throttle > 128 + dead ] ) then
forward = false;
backward = true;
else
forward = false;
backward = false;
endif endif
You may need to adjust the joystick number if your profile has other joysticks than the Pro Throttle. You can also increase/decrease the deadzone to your liking.
To make the profile actually send the keystrokes, just program the buttons 1 and 2 of the CMS controller.
Have fun!