It will not be easy since it is a very complex protocol, with a complicated CRC and duplicated bytes, meaning variable-length messages. It is not easy to know in advance how many bytes the reply will have. I implemented it using the 761 communication manual. If you have the manual and are well experienced with rs-232, I think you should be able to make it work soon.
If you are in a hurry to solve your problem, I suggest that you invest USD 299 to get a single user license of my ActiveX product TAS-HMITalk which curently includes a driver to communicate VB6 with Fox761 in a straight forward way. The product is available in my page http://www.nivaltec.com. Let me know if you are interested.
