The parameter wire dialog should popup.

Take some time to look at what's happening here, you can clearly see that path constraint>percent is selected under bone01 and the Y Position for position_icon is selected, now hit the arrow in the middle, pointing to bone01, then Connect, sooo now you are controlling bone01 path percent with position_icon Y position:)

If you move your position_icon, you will notice that your track is racing around, hmm not so good, so here's what I do:
Just divide "/" by a value, say 50, then 100, maybe 300. Yep, you guessed it, just play with a value till the track stops sliding when on the ground plane. I got to a value of /350. Remember to hit update everytime you change the value.

Select all the track_parts, bones, and track_spline and duplicate, unfortunately max doesn't maintain the wiring connection on the duplicate, so go back and repeat the wire setup or, open your maxscript listener and select:

paramWire.connect $'position icon'.pos.controller[#Y_Position]$Bone01.transform.controller.FK_Sub_Control.controller.
Position.controller.Path_Constraint.controller[#Percent] "Y_Position/350"

Copy from the pink and paste it in the white/grey area, change the $Bone01, to the name of the red bone on the second track (mine is $Bone37), hit enter.

And there you got two easy to animate tracks! Lets add some wheels using orientation constraints and wiring.