Change color of rows every time value in first column changes

[Natasha]

Hi,
I am using Excel 2003.
I have a spreadsheet with one-to-many relationship data. First column
contains plot numbers that repeat if more than one species of plants were
found at that plot, i.e. plot number can be repeated an unspecified number of
times. I am trying perform a function that is similar to highlighting every
other row, except I would like to highlight every other plot. Thanks!

 

[Don Guillett]

Example of layout

 

[T. Valko]

Is this what you want:

1 = shade
1 = shade
2
3 = shade
3 = shade
3 = sahde
4
4
5 = shade
6
6
7 = shade
7 = shade

If so, assuming your data starts is in the range A2:A20

Select the range A2:A20
Goto the menu format>Condtional Formatting
Select the Formula Is option
Enter this formula in the box on the right:

=MOD(ROUND(SUMPRODUCT((A$2:A2<>"")/COUNTIF(A$2:A2,A$2:A2)),0),2)

Click the Format button
Select the desired style(s)
OK out