Hi all,
I think this is challenge issue, as I think it's pretty hard solvable, and I don't have much experience to play with this, but it would be very useful feature if accomplished... For a start let it be not dynamic, but just like standard offset, you specify distance and side for offset and it'll do just some edges, but be aware that chained edges should be trimmed/extended adequate like it's doing built-in offset command... Maybe I overlooked something, but I don't need pure lisping, I want to say that every method is allowed - using other known and unknown commands, functions etc... If it's not a problem, it's allowed to be used OFFSET built-in command to accomplish similar result, just rename main function name to something like "selectiveoffset" or something... This task should be applicable only for polygonal open/closed pline edges (LWPOLYLINE)... Selected edges should be highlighted or made visible by picking using BLIPMODE = 1, or any other method you think of for creating adequate selection and previewing that selection of edges...
So lets see if it's doable,
I wish you good luck, and happy coding,
Regards, M.R.