I do not know of any software for this. It might be tough to do, since LISP can do some things that VBA cannot and vice-versa. There is a programming comparison matrix in the help file in AutoCAD that can help you see what differences there are with LISP and VBA. With the addition of VisualLisp now, a lot of the object programming of VBA is now available to LISP. You will probably need to pick and choose what to convert. Not all programs have to be converted unless you need some different functionality. We use LISP and VB along side each other just fine.
"Everybody is ignorant, only on different subjects." — Will Rogers