Split values in Cell D onto next line??

[JohnSmith]

My Excel spreadsheet is setup like this:

Cell A Cell B Cell C Cell D
John Smith Yes Alberta,Ontario,Quebec

How can I code it so that I can turn that into this:

Cell A Cell B Cell C Cell D
John Smith Yes Alberta
John Smith Yes Ontario
John Smith Yes Quebec

Basically take the values in Cell D (where there is a comma) and it add to the next row containing the other values in Cell A, B, and C

Help is appreciated.....

Johnny