A method of dynamically allocating usage of a shared resource between user A and user B includes the steps of establishing an initial allocation percentage for user B for using the shared resource and establishing a threshold allocation percentage for user B. The allocation percentage is modified for user B based on the availability of the shared resource to user A. If the shared resource is unavailable to user A, the allocation percentage for user B is decreased. If the shared resource is available to user A, the allocation percentage for user B is increased. Usage of the shared resource by user B is allocated in accordance with the modified allocation percentage provided that the modified allocation percentage is less than a pre-set threshold level. The method is particularly useful in dynamically allocating telephone calls into call centers.