Split One Large Dollar Amount To Multiple Cells?

I have a group trip coming up where we took in a $1000 deposit per person. The total amount is only in the main members cell. There will be two more payment amounts coming. I need to make certain each person has paid the total amount they are required for the trip. There are two possibilities for total trip amount. Double occupancy is $15,500.00 and Triple is $14,500 per person.

There is a unique Identifier for each registrant, except when there is a multiple person under one registration the identifier has all the same number except at the end. I figured out a way to strip the number down to just show the same number in one registered group. There could be up to 10 people under one registration. I might not have the best option for breaking down the Identifier number, but thought it would be a good start. Used the code Left(column, number).

Issue is this. How can I now take the total number of people under one group take the total deposit and split it between just that unique group so I can then determine what is still owed after payments are made.