Help with clearing cells with duplicate data without deleting the entire row

Hey all,

I'm needing a bit of help deleting duplicate cells without deleting the entire row of data.

For example I need to turn this:
Code, Product, Colour
AB121, Camelbak Coloured Valve, Black
AB122, Camelbak Coloured Valve, Blue
AB123, Camelbak Coloured Valve, Red
AB124, Camelbak Coloured Valve, Green

into this:
Code, Product, Colour
AB121, Camelbak Coloured Valve, Black
AB122, , Blue
AB123, , Red
AB124, , Green


I need to be able to put it into a macro so a little bit of coding would be hugely appretiated.

Thanks
Dave