I was wondering if anyone knows if it's possible to set the background colour for the rows in a list depending on what the cell values are. See bellow...

Z1 A1
Z1 A1
Z1 A1
Z1 A2
Z1 A2
Z1 A2
Z1 A3
Z1 A3
Z1 A3
Z1 A4
Z1 A4
Z1 A4


I have tried to illustrate this as best I can. If the above list represents the first collumn in a spreadsheet the row colours need to alternate as illustrated. There should only be two colours in the spreadsheet. This is just a way to seperate the different entries according to the first row instead of using borders.

If anyone knows how it could be approached that'd be great

Alex