Is it possible to tell a device to use the ADSL connected to WAN2 instead of WAN1. Both WANs have an active ADSL connection.

I have told the router to use wan 2 for one ip range and wan 1 for another. Each is then set to fall back to the other in case of malfunction. Its then just a matter of fixing an IP address to the mac number of the device and then they will keep to their own wan. I'm not sure this is the most elegent solution but it works well.

Thanks for the info, i'll give it a go

You can also set a load balance property to route "all" traffic via a wan of your choice (or specific traffic, such as all port 80 and 443 etc)