Formula for showing dates for next service due vehicle

Hi All,

I am looking for a formula to show me the next service due date for vehicles. For example please check below

Date Customer Name Vehicle Name Service Due

1-Sep-14 Mr. ABC MH20 U678 The formula over here should calculate date after 3 months ie Nov '14

10-Oct-14 Mr. XYZ MH16 I564 The formula over here should calculate date after 3 months ie Dec '14

20-Nov-14 Mr. LMP MH20 L234 The formula over here should calculate date after 3 months ie Jan '15

We can keep the vehicle name as the unique id.

Awaiting for response.

Noted, Thank you Special-K