Group Expense Splitting into couples

Hey everyone, I needed some help figuring out if its possible to split this group expense formate into couples. I managed to do so myself but it gets tricky since one of the group expenses 1 our of 4 is not liable to pay so how can this formula work correctly in this type of situation? for example if Chris paid for a hotel $300 but only 3 out of the 4 will need to pay they would owe him $100 now if he also paid for a car rental that is $400 split x 4 everyone owes $100each so the other couple should owe Chris $300. the current formula does not show that.