I guess you mean the outgoing caler ID, as long as you insert the whole number in the Incoming call routes when configuring your direct dial numbers the system will forward that number when making calls. Thats in NZ anyway, if not you can use the short code
Short Code ?
Tel Number .s "Number" (No speech marks required)
Line 0
Feature Dial
Soopa Doopa Intergalactic IP Office installation mechanic and configuration corruptor from way back.