I need to calculate usual CRC16 (polynom 0x8005) in VFP.

VFP SYS(2007) and Bob Herguth source code in
http://fox.wikis.com/wc.dll?Wiki~CRC16~SoftwareEng will calculate only
CRC-CCITT (polynom 0x1021) checksum.

Any idea how to calculate "usual" CRC16 ?

Is it possible to modify Bob Herguth source code or use some other function ?