I have data in the following columns:
a b c d e f
g h
date name unit start end booking payment
balance
01/06/09 John Smith 1 1/10/09 10/10/09 $1000 $100 $900
01/07/09 John Smith 1 1/10/09 10/10/09 $500 $400
15/09/09 John Smith 1 1/10/09 10/10/09 $400 paid
01/04/09 Mary Jane 4 1/11/09 20/11/09 $2000 $1000 $1000
21/05/09 Mary Jane 4 1/11/09 20/11/09 $1000 paid
01/10/09 Fred Mac 2 1/12/09 02/12/09 $200 $200 paid

I need to create a balance sheet for each booking calculating the amount
outstanding. Each time a payment is made a new line is created showing the
date and the amount paid. This is then subtracted from the initial booking
and you are left with the remaining balance owing or the text "paid".

I have tried nested if statements but it is getting too confusing to sort it
out as the number of payments can vary from 1 to many payments.

Can you help simplify a formula to solve this problem.