Hi!
I would have been tempted to go that way but if @danielf suggested the other way he probably saw a reason why this would not work...
(I am assuming all the formatting stuff but I could be wrong...)
Actually I am pretty sure this will do exactly what he wants...
When you call a Germany number from Germany do you prefix it with the country code?
I am not from there but I am pretty sure that you don't so the only times he will attempt to call from Germany a German number prefixed with the country code is when the phone number comes from his LDAP server...
So it sounds to me that what @danielf provided him will work as he wants...
Have a nice day!
Nick