JB, how about this. I'm a machine shop mechanic, and I've seen something like this done in a milling machine t-slots. Most metal cutting milling machines, have similar looking t-slots in their work table. I seen one shops set up where they locked down a t-bolt, using a large set-screw where you would usually have a t-bolt, at the end of the table (t-track). Then, they machined precision bars that fit in, but came above the t-slot. Where one end would hit the screwed down t-bolt, and the other end came up high enough out of the t-slot, to hit the plate they wanted to machine. Their plate, being your fence. You would make yourself a series of pairs of these bars, to the different lengths that you want your fence to stop at. They just sit in the slot, sandwiched between the dead t-nut, and your fence. Put, say a 4" long set of bars in there for one setup. Then take those out and put a longer set in, to move the fence forward. Make yourself a nice box to keep your sets of bars in, or put a whole in the ends of them and hang'em on a wall. Mark each one with the length that they set your fence at.
Dang, I think I just talked myself into making a setup like that myself!! Thanks!! LOL