How to automatically increment periods by one month with different start dates

Dear All,

I have an excel want to record receivables from ten more payers, they need to pay monthly but start with different start dates.
For example a payer Apple needs to pay on first day of each month starting 2013-5-1, Mary needs to pay on every 12th starting from May; and John pays on every 28th starting from May as well. I have a column marking the date (from and to), e.g. for Apple I mark as 2013-5-1 to 2013-5-31 to show the payment period; Mary's payment period is 2013-5-12 to 2013-6-11; while John's payment period is 2013-5-28 to 2013-6-27.

How can I make each payment period increment automatically? Please see my attached excel. Thanks!