Mask effect with smoke

Hi guys .
this is my problem…I’m beginner in flash so ,hm…
anyway I want to achieve smoke mask but it doesn’t look realistic so I was wondering is it posible to do this .
I have two images one black&white and the other one is color and with mask I reveal the color picture and for that I’m using mask ( best solution is something like smoke)
any sugestions ?

ps sorry for mistakes

cheers Leo