Using conditional formatting to group items

I have a list of items in a column that appear in small groups.
In column a there may be: apples, apples, apples, bananas, bananas, oranges.
I want to have a thin line appear between like items and a heavy line between dissimilar items to create “groups” visually.

I set ALL the horizontal borders to heavy, and set up a conditional format that compares each row to the previous one and if they match it changes the top border in that cell to a thin line. My conditional formula in cell A3 is simply...
=$A3=$A2

It works fine in 2010, But not in 2007. I can find no reason it shouldn’t work equally well in both. In fact I find that conditional formatting of borders in 2007 is hit or miss. Anyone else have this issue?

Thanks, but I tried that initially. Doesn't make a difference.

My method works fine in all versions beyond 2007, so I'm calling it solved.