sleep mode

[zongo saiba]

Hi, 

I have set up my unit Ubuntu 9.10 to go to sleep after 5 minutes when
inactive. I have a notebook and want to maximize ny battery life. When I
use skype with video (or just voip calls), my unit still goes to sleep
after 5 minutes not detecting the fact that it is being used. 
Anyone has any idea on how to make sure that the OS actually picks yp
the unit being in use and not putting it to sleep ? 

Kind Regards,