NLB doesnt have anything to do with subnets. as long as you have proper routes in place to enable the subnets talk to each other, creating the NLB would be exactly similar to creating nlb on same subnet.
as for how to create NLB on 2008 R2 - please see
http://technet.microsoft.com/en-us/library/cc754833(WS.10).aspxit has enough resources to get you started. please read the whole thing instead of trying to get it up and running asap else you may have issues later.