Is there anyway to route Skype over different WAN?

Hello, I have a Fortigate 200B with 2 X WAN`s. WAN1 - Primary WAN WAN2 - Secondary WAN Ipv4 policy is set that all traffic goes through WAN1 I would like that Skype will always go through WAN2 Is such thing is possible? Maybe with ToS or DSCP via Policy Routing?

I know skype is MSNP24 

I have windows Network. thanks.