Something like this:
function MyLeetVehicleData::OnTrigger(%this, %obj, %triggerNum, %val)
{
if(%val) //1 = trigger down, 0 = trigger up
if(%triggerNum == 2) //2 = jump trigger
//do stuff...
}
Jump, shoot, crouch, and jet all use triggers and will fire this callback when activated. You might have to do vehicle::ontrigger or wheeledvehicle::ontrigger instead. Experiment.