Excel forumla for decending money

I currently own a home with some roommates and want to create a simple excel spreadsheet that would caculate the total amount they give me and apply it to the bills in order of importance. Roomate 1 gives me 1000, I want to take that 1000 and subtract it from one row for rent - 500 then take this total and apply it to the next row - Electric - 30, then that total is caculated and then applied to the next row for Gas -50, then that total is caculated and then applied to the next row cable 150, then that total is caculated then that total is subtracted to the next row - food and enternatinment - 200. which then gives me a total of what is still owed if any.

Given = 1000
rent = 500 paid = 500 = owe = 0
electric = 30 paid = 30 = owe = 0
gas = 50 = owed = 0
entertainment = 200 = owed =0
total = 220 overpaid

Please find the xls file attached to see if it would be helpful to you