[Zope] Creating graphs with Zope (under NT)

How are the Zope website statistics graphs created? I need to create simple graphs (pie charts and line graphs) from data held in an ODBC database, using Zope under NT (unfortunately). I looked at gnuplot, and found ways to produce really impressive complex sophisticated graphs, but nothing to produce simple pie charts. Did I not look hard enough? Is there a better way? The charts do not have to be live - the information changes at known times weekly, so I could run external processes to create image files that are served using LocalFS, if necessary. Thanks, Richard