I think Derek is right. if you are using enterPath then you should be able to update the rubberband preview as you like. below is an example
'enterPath ?prompts list("Enter Points","Enter next Point")
this is just the callback procedure in a createBus skill. the rubberband width is defined by the ?pathWidth which is kept updated everytime a user changes one of the input (for example width of wire or spacing between wires of a bus channel).
The cmdName "bbbb" I have used to avoid nesting of enterfunction, in-case user hits the assigned bindkey several times.
I hope this helps.