duplicate vray framebuffer

i am wondering if there isn`t any workaround/script that allows to duplicate vray framebuffer ???
while working in linear space the “duplicate to max framebuffer” option is not a solution in our workflow because the gamma in maxframebuffer is multiplied and displayed too bright.

You may be able to get by with the undocumented render history function of the VFB see http://www.chaosgroup.com/forums/vbulletin/showpost.php?p=358321&postcount=26

thank you eric for your supply, now i know how to create an evironment variable under windows ;-)…thats a great support to our workflow and i wonder how many undocumented things i 've missed obviously :-o …thx alot !!!
@vlado : please, this ist the most needed button ever!!!