[Ziaholic]

Here's a shot of something that doesn't do exactly what you want, but it's close and easily modifyable ... our trigger overrides the throttle and sets it to full speed.

In the pic, the case structure shows the FALSE case, where the throttle goes straight thru, but when button 1 is pressed, the TRUE case has a hard constant 1.0 wired up into the throttle output of that case structure, ignoring the actual joystick throttle until the button is released.

In your case, you'd wanna' wire up a 0.5 constant to it, if you want half-speed.