You could make a script for the object that checked the PLRDISTWITHIN condition and displayed a series of HUDs depending on the distance. If you use image HUDs (like a graphic representation of a meter) you need to make a HUD for each distance you wanted to represent. If you want to use plain text HUD, you could use the FPGCRAWTEXT command.
That's the theory part of it.
The object would of course have to be dynamic and probably always active. It would look something like this:
;Artificial Intelligence Script
;Header
desc = display player distance)
;Triggers
:state=0:state=1
:state=1,plrdistwithin=500:[code to display 500]
:state=1,plrdistwithin=400:[code to display 400]
:state=1,plrdistwithin=300:[code to display 300]
:state=1,plrdistwithin=200:[code to display 200]
:state=1,plrdistwithin=100:[code to display 100]
:state=1,plrdistwithin=50:[code to display found it]
;End of Script
Brian.