Document for Custom graphs.

Hi,

I am new to xymon, till now my experience is superb with xymon. I am able to do whatever i want, i have customized the xymon starting from html pages till adding extra scripts on client. As a further customizing i am looking to draw graphs for my customized script. 

Can you please let me know where i can get a doc or link for customized graphs in xymon.

Thanks....

Regards 
Gautam