Sony RM-VL710 Universal Remote

Help! This is a great remote, but I want
to "unlearn" 2 buttons that I taught from my
TIVO remote. I can't get it to 'unlearn'. The
manual isn't clear.I push 'SET' then I push 'CBL'
at the same time pushing the button I want it to
unlearn. Well now the button does nothing but it won't let me 'teach' it either. How long do I have to hold both buttons down? Which lights go out?
If anyone is familiar with this remote I would appreciate any help.
thank you, Mary