adding new licence to existing one plese help !

Hello
I have got ADNM and licence.dat for 17 network and proffesional clients valid to 6 december 2007 . We have additional 5 workstaions without avast and I would like to add tem but I need licence.
What should I do buy new licence for 5 workstations? and add this to existing one ? Or buy licence for 17+5=22 workstation ???
Can ADNM import more then one licence.dat ???

Please touch base with our sales team (sales@avast.com).

Thanks
Vlk