Number generation

i have a e1 trunk connected to my asterisk server. i got 30 number from my vendor. how can i generate these 30 number randomly as my number when i am making outgoing calls. please help me urgently…

voip-info.org/wiki/index.php … +func+RAND ,
voip-info.org/wiki/view/Aste … c+callerid .

Cheers.

Marco Bruni
www.marcobruni.net