Given that you are mentioning FASTAVR and BASCOM (assuming the AVR version), my first guess would be no. I would still see if it could happen.
If it is on the PC side (there is C and BASCOM there), yes it can be done. There is a calling convention change (from the stack perspective) and there are a few simple flags to change it. This is available because M$ controlled most of the compiler technology early and everyone adopted the same formats. This has not been the case in the embedded world.
robotman