You could use a sensor from an external device. I can't remember exactly which front panel it was, but the Thermaltake Hardcano series might be it. I think they have temperature sensors that you can place on your GFX card:
<A HREF="http://www.thermaltake.com/products/hdcoolerMenu.htm" target="_new">http://www.thermaltake.com/products/hdcoolerMenu.htm</A>
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<A HREF="http://www.khmercity.com/city_music//Kerpal Comedy@@ kick my dog~
/Jerky Boys - Kerpal - Airport Pakistani And Hindi Fight.mp3" target="_new">I'm going to get you, you bastard guy</A>.