Dueling sphere

Create a sphere with a 20 foot radius centered on yourself of whithen 5 feet of yourself only people of equal or higher challenge rating are allowed in this sphere for player challenge rating use your level.  Anybody who would be in this sphere but is not of a high enough challenge rating is pushed to the nearest safe space if there is no safe space whithan 50ft they are still shunted to the nearest safe space but they take 1d8 force damage.  People who have enough strength may enter the sphere simply by walking in but none can leave until the spell ends. And no spell of a lower level then the slot used to cast this spell may leave or enter the sphere.

for every level of slot higher then 5th increase the radius of the sphere by 5ft for ex casting using a 6th level spell slot will have a radius of 25ft