How do I run and stab in BFBC2?

I always have to stop and stab, while other players stab right throw me and their feet never stop moving.How do I run and stab in BFBC2?
You don't have to stop and stab but it is trickier than usual. You'll just have to make sure your aiming correctly on the opponent and get close enough to initiate the stab. It takes a lot of practice to get use to it, eventually you'll be running and stabbing like nobody's business.