using "super" or "hyper" keys as "ctrl+meta"

While remapping my keyboard to get an optimized layout for work with
XEmacs [1], I am wondering whether it is possible to use a single key
for the combination control+meta.

I think in X windows it is impossible to get a key producing both
Ctrl and Meta (Mod4 in my config) modifiers.

So the only way would be mapping a key as Super (or Hyper) and let
Emacs translate Super to Ctrl+Meta, that is, \s-a would be translated
to \C-M-a.

The Ctrl-Meta combination is so usual in XEmacs that I find strange
that I could not find any similar idea in EmacsWiki.org and other
XEmacs-related webs.

Has anybody seen something similar?

Thank you very much.

	carlos

-- 

[1] So far, I have my Spanish/Spain PC105 keyboard changed like this:

using US layout (better for programming and TeX writing)
< > (less/greater) -> ESC (at the left of Z, for VIPER mode)
Caps Lock -> Ctrl (usual change, could be Super)
ESC -> Caps Lock (could be Hyper)
Alt, AltGr -> Ctrl (as in Lisp machines)
Win -> Meta (usual change, and Lisp machines)
Menu -> Compose (usual change, for Spanish/Esperanto symbols)
Ctrl -> Alt (that is, swapped Ctrl and Alt)
[] <-> () (that is, swapped parentheses and square brackets, for
           easier Lisp editing)

_________________________________________________________________________

Carlos Enrique Carleos Artime                             ,  GNU.org  , 
Dep-to de Statistiko kaj Operacia Esplorado,             /             \ 
          kaj Matematika Didaktiko                      ((__-^^-,-^^-__)) 
Universitato de Oviedo                                   `-_---' `---_-' 
                                                          `--|o` 'o|--' 
Retposhto: [email protected]                                 \  `  / 
Telefono:  +34 985 181 904                                    ): :( 
Fakso:     +34 985 181 902                                    :o_o: 
Adreso: Escuela de Marina Civil, 33203 Hispanio                "-"