It is my understanding that vla-copy works differently than command copy. If you use copy "m" and try to copy objects at a set distance like every 4 feet, you have to type 4' 8' 16', whereas if you use copym from express tools you can achieve the same thing by typing 4' 4' 4' or 4' repeat, etc. This is achieved through vla-copy and vla-move. It sounds like that is what you're after.
As I reread, maybe not, but it should give you something to think about.