Complicated escape (or two escapes) or some other answer.

Hello, all,

  To save my pinky, I've gotten accustomed to just plain F5 as my escape
key.  On this new Inspiron 1010 that my work gave me, you have to hold
down the blue 'Fn' key while pressing what ought to be F5 to get it to
be F5.  It's default behavior is described by 'xbindkeys -k' as

   Mod2 + XF86MonBrightnessUp

I'd like to make that my escape key for this machine.

  Worse still, when I plug in an external keyboard which lacks the
innovative XF86MonBrightnessUp key, I'd like plain old F5 to be the
escape key.

  I told xbindkeys to make the weird key do

ratpoison -c "readkey root"

  which emulates the true escape key except for my most used feature,
pressing the escape key twice to go back to the previous window.

Any ideas how to get out of this bind?

 Sincerely yours,
   John B.