MTGNexus

If I have a creature with "can block any number of creatures" and another with banding how do they interact with each other?

Unless I am misunderstanding what you are trying to do, there is no special interaction here. You use Avatar of Hope to block 5 creatures. You then use the Banding creature to block one of the same creatures as the Avatar. For that attacking creature, and that creature only (since it is the only one blocked by a creature with Banding), you get to decide on how combat damage is assigned. You can choose to have all assigned to the Avatar, all assigned to the creature with Banding, or some other distribution of damage. It doesn't really matter if the Avatar is blocking other creatures. Those will deal damage to the Avatar as normal or the normal rules for damage assignment apply in the event that the Avatar is not the only blocker of the other 4 creatures (assuming no creatures with Banding are blocking other attacking creatures).