How do you increase the 7D ISO to 12800?

[mynewromantica]

For the life of me I cannot figure out how to extend the ISO on the 7D to 12800. I know it is possible but I can't figure it out. Has anyone had success with this?

 

[iBookG4user]

It's in the Custom Functions. C.Fn I and then set #3 to on.