creating custom graphs

I have some Solaris servers that I can't install the xymon binaries on so I'm going to try writing my own scripts to replicate the default xymon data. I successfully tested sending messages directly to port 1984 from my client to my xymon server, but I'm not clear on how data that is in graphs is sent/generated. For instance, if I wanted to generate a cpu graph, I can send the cpu values but I'm not sure what I would then need to do in order to generate the rrd graphs. Can anyone point me toward any documentation for this?

thanks, EJ