Debtor Days Countback method
 

Hi, I am looking for some help trying to calculate debtor days using the countback method.

I have a spreadsheet that shows invoices and outstanding debtors month by month and need to calculate the how many days the outstanding debt represents using the countback method.

My figures are contained in columns representing the months (B7:O7), with the month end debtor totals in row 8 and invoiced amounts in row 9. I would like to include the debtor days in row 10.

Grateful for any help.