Angel, I feel for you. Border Collies need something to herd, and pretty much anything will do. I've got the same problem with my 14 month old Fila Brasileiro, Kharma. She won't stop herding the cows until she's got them all in one place - every single solitary one of them. So now she doesn't get to go out and run with the other dogs until after dark, which really isn't a solution for a Border Collie, as coyotes are a problem in just about every rural area in North America now and a Border Collie isn't equipped to take on a pack of coyotes.
Have you tried to find some good training materials on herding/droving? That's the next thing I'm going to have to do. Training a BC should be easier than training a Fila since BCs were bred to follow orders and Filas were bred to work on their own.