MsOf10 Excel VB to insert rows until cells match

Hi, I was hoping someone could help me with some VB that will insert cells in Columns B, C & D until Columns A & B match each other.

For Example my data looks like this:
Col. A Col. B Col. C Col. D
G1 G1 red yes
G2 G4 purple yes
G3 G5 green no
G4 G7 red no
G5 G9 green yes
G6
G7
G8
G9
G10

And I need it to look like this:
Col. A Col. B Col. C Col. D
G1 G1 red yes
G2 <----2 rows insterted here
G3
G4 G4 purple yes
G5 G5 green no
G6 <----1 row insterted here
G7 G7 red no
G8 <----1 row insterted here
G9 G9 green yes
G10

The values in Column A will never change. The values in Column B are always in numeric order so I don't have to worry about sorting anything.

Thank you so much for your help! I really appreaciate it!