conditional cell shading when a change occurs

Hi! Just recently joined this newsgroup, in hope that I can find an answer to my problem. I am generally familiar with Excel, but need some help on this particular problem.

I want to apply a format where whenever the number in a column differs from the one previous to it, a cell shading color change is applied.

For example, you have a column of numbers in Excel:

2
2
2
5 (cell shading color change applied)
5
5
5
2 (cell shading color change applied)
2
2
3 (cell shading color change applied)
etc....

It doesn't matter what color is used, just so that it is applied whenever there is a change from the previous number.

There has got to be an easy answer to this.... thanks so much in advance for any help!