Filled radar chart with multiple series

I have a filled radar chart with two series that partly overlap. Unfortunately, one series covers the other and some information is lost. Is there a way to make the area covered by one of the series transparent instead of solid color? Thanks for the help.

Anyone who looked and thought about this ... thanks.

I found the answers at Peltier's website http://peltiertech.com/Excel/Charts/VBAdrawradar.html

There are 2 parts to the answer:
(1) transparent chart series fills are not supported by Excel versions prior to 2007

(2) Peltier gives VBA code which will draw polygonal shapes into the radar chart series, using each point in the series as a node; then, color the overlap areas to give the effect of intersection of transparent regions.

Brilliant! Wish I had thought of it myself.

- Pete