Upgrade C++ ARX Files to work in 64-bit environment

We have Object ARX files which were written in C++ approximately 7-10 years ago to work with AutoCAD 2000 and AutoCAD 2004. As we are upgrading our systems from 32-bit to 64-bit we need to also upgrade these files to run in the 64-bit environment. We are looking for someone that has worked with ARX programming before and has experience with upgrading C++ source code. We may also need an update for a Visual Basic program that draws on information from these ARX files/AutoCAD in general. There are approximately 20 files/functions in total and we would need someone that can start working on this asap. Please contact for further details.