u need 4 midi out channels..and assign each virus channel to one midi out channel...set the same port number on midi channels as the snow....
if u want to process them seperately, u need to go into the configuration page in your VsT wrapper for the virus and select the mixer channels for each of the virus outputs....
i know how to do all this in fruity loops ...what are u using?? sonar...i dont know..but it will be similar...
EDIT :
ok i've uploaded a video for you...but it will show u how its done in fruity...u will need to figure out how to do it in sonar..
http://www.youtube.com/watch?v=lQ5WyuQH8c8