How to combine accidental glyphs for new note names?

[pls]

Hey all,

I'd like to be able to call some rare accidentals by their own note names. For 
example "ceseses" should result in a triple flatted note c.  I found a very 
useful snippet: http://lsr.dsi.unimi.it/LSR/Snippet?id=784.  I just added three 
lines to test the new note name and it basically works (here I kept the old 
variable names.):

#(define-public TRIPLE-FLAT -15/10)

arrowedPitchNames = #'(
    (ceseses . ,(ly:make-pitch -1 0 TRIPLE-FLAT))
; […]
)

arrowGlyphs = #'(
; […]
    (,TRIPLE-FLAT . "accidentals.flatflat")
)

{
  ceseses'
}

Not surprisingly the result is a double flat sign.  LilyPond does not have a 
glyph for a triple flat (probably because it's so rare), so I tried to combine 
accidentals in a couple of ways but none of them were sucessful, e.g.:
    (,TRIPLE-FLAT . ("accidentals.flat" "accidentals.flatflat"))

So is it possible at all to associate several values to one key in scheme?  It 
probably is.  I guess I simply defined a list in a list which leads to an 
error.  But what would be the right way to define a combination of several 
accidental glyphs for a new note name?

Thanks for your help!
patrick