I need to remove the ultrakey from a rectangle

Hi all, so my wife volunteered me to edit the local school video in the absence of a panto this year. I am ok with premier pro and green screen all the time. However, they used a similar colour clipboard to the greenscreen without knowing so i am losing a key bit of video when i apply the ultrakey. The bit i need to mask does not move much and it does not need to be perfect, any way i can apply a "dont ultrakey" this bit easily? 

so in summary, i have the video, i put on the ultrakey, then i need to remove the ultrakey from a rectangle. I am against the clock so any help appreciated. 

thanks

[title edited by mod]

Darren.