x-symbol like ASCII token replacement

[Achim D. Brucker]

Hi,
I'm searching a way for getting a token-replacement similar to 
the one the x-symbol-mode provides, e.g. when using x-symbol 
with the LaTeX token language I can write "\textasciitile"
and get "~" displayed (whereas a saving this file and copy/paste
still used the "\textasciitile" representation). I already 
extended the x-symbol mode for my own symbols, but now I 
want to replace a token by a multi-charakter symbol, e.g.
when I write "\textasciitile" the text "tilde" should be
displayed (but of course, \textasciitilde should be stored in 
the file, etc).

It seems that this is not possible by simply extending a 
x-symbol token language. Do you have any hint's how I 
could achieve my goal?

Thanks,
        Achim