belt drive

hi everybody - in an animation I want to show a belt drive with six wheels. To show the wheels rotating is easy, while showing the belt moving is not satisfactory for me until now. I used the funcion 'oscillate' from the effects dropdown menue, but now it looks like a Micky Mouse drive, where the belt nearly jumps off the wheels. Is there a chance to manipulate the effects more precisely? For example, if the belt would only show a very slight movement, then the illusion of a driving belt would be perfect.