Global variables - how global are they?

I want to declare variables as global (or call them constants if you want) but they need to be global accross all .conf files. It seems that the variables in the [global] context in extensions.conf is only global within extensions. (for that matter they not global :smile: )
I want to be able to access a global variable within my sip.conf and voicemail.conf for example. Is it possible and if, how do I do that?

Bump - nobody have an answer to this?