How to make following periodic billing

Dear experts,

I have a billing scenario need your help.

Billing plan for a long term service.

For example: contract: 2012 Sep 20 to 2012 Dec 10

The expected billing plan would be following:

2012 Sep 20 - 2012 Oct 19 (full month)

2012 Oct 20 - 2012 Nov 19 (full month)

2012 Nov 20 - 2012 Nov 30 (month before the contract end. not full month)

2012 Dec 1 - 2012 Dec 10 (contract ending month, not full month)

I know the straight forward billing plan would be billing every month and last invoice will be for days left. But in my scenario, the last two invoices will be not full month.

How to make it happen?

Thank you!