Force to use a specific codec only for specific calls

Hello,

in the Sip.conf I can specify what codecs are allowed/disallowed (for the whole environment or for single user)

But my question is: can I force to use a specific codec only for specific calls?
I mean, the user XXX has the following configuration:
disallow=all
allow=ilbc
allow=gsm
… Is there some way to force to use the only the codec gsm when XXX calls the number YYY ?
Tks