VQ Plus Queue callback module

When the caller is called through the queue callback module...they are place in row in the queue but if a call is assigned to the agemt while the queue callback is calling.. the callback call is place in second in the queue instead of being prioritize which make another waiting and frustrate the person being called and they have to wait for the agent to be available again... how can we avoid that and not assigned any call while the callback is calling.... if no answer than we can assign a new call and try later that person.