Animating hand along a straight axis in Poser

Hey SL peeps! I'm new and this is my first post so be nice

Anyway, I'm well underway creating my first proper scripted object, which is going to be a playable trombone. Through labourious trial and error, I've managed to get a decent animation for the default holding pose via poser.

However, the animation of this object is largely going to depend on a secondary attachment for the main slide (the bit you pull in and out to play the trombone) on the right hand and the rest (mouthpiece, bell, etc...) on the left hand.

Thus, my question is: How (in poser) can I animate the right hand pushing out and pulling in along a perfectly straight axis? Obviously if I made key frames for the innermost position and outermost positions, poser would tween the frames with the hand deviating from this axis of movement thus ruining the look of my trombone. If I'm not explaining this very clearly, have a look at the image I've attached to this post which illustrates my problem more clearly.

Thanks in advance!

Use IK. Although IK for the hand is off by default, you can turn it on; it'll work just like the feet.

Thanks for the reply Johan, that was really helpful

(...and now I know what IK is/does )

Also (and sorry if you know this), use the numbers to move the hand on one axis, as opposed to just dragging it in the preview window - sometimes dragging a body part takes it off in all sorts of directions.

If you already know that, ignore. If you don't know what I'm talking about, either someone else with Poser to hand (or a better memory) can explain, or I will when I have it open next!

Nice trombone btw. Did you build that?