Changing Shading when a Column Value Changes

Doug has a data table that includes a column of part numbers. This data is sorted by the part numbers column. The part numbers are not unique; for instance, some part numbers appear three times in the table and others appear five times. Doug would like to format the table so that the rows of the table have a "green bar" effect.

For instance, the first five rows may have the same part number, so Doug wants those rows to be shaded green. The next two rows have a different part number, so he wants those to have no green shading. The next three rows have the next part number, so those should be green again, and so on. Every time the part number changes, the shading of the row (green or not green) should change.

One easy way to accomplish this task is to create a helper column that displays either a 0 or a 1 depending upon the part number in column A. For instance, let's say you wanted to put your helper column in column Z. You could put the following formula in cell Z2:

=IF(A2=A1,Z1,1-Z1)

Copy the formula down column Z for each row in your data table. When done, column Z will contain either 1 or 0, switching only when the part number in column A changes. You can then use the value in column Z as a controlling value for your conditional formatting. All you need to do is set the formula in the format so that if column Z contains 1, then your cells are green.

You should note that once your conditional formatting is set up and working properly, you can hide column Z so that it isn't a distraction to anyone using your data table.

If you can't use a helper column for some reason, then there is a pretty cool formula you can use in the conditional format itself. Just make sure your data table is sorted by column A (the part numbers) and then select all the cells in the table, with the exception of any column headers. Then define a conditional format that uses this formula:

=MOD(SUMPRODUCT(--(($A$1:INDIRECT(ADDRESS(ROW()-1,1,3,1))
=$A$2:INDIRECT(ADDRESS(ROW(),1,3,1)))=FALSE)),2)

Remember that this is a single formula, entered in the conditional formatting rule, all on one line. This formula assumes that the part numbers are in column A and that the data table begins in cell A2. Further, if you delete any rows in the data table, you'll want to reapply the conditional format to all the cells in the data table.

Finally, there are any number of macros that you could write to apply the formatting. All you need to do is have the macro step through the cells in column A, determining whether the part number changes, and then apply the correct formatting based on what it finds out. Here is an example:

Sub ShadeRows()
    Dim ThisOrder As Long
    Dim PrvOrder As Long
    Dim LastRow As Long
    Dim Clr As Integer
    Dim R As Long

    LastRow = ActiveSheet.Range("A" & Rows.Count).End(xlUp).Row

    ' Enter desired color codes here
    ' (24 is Lavender, 35 is Light Green)
    RwColor = Array(24, 35)

    Clr = 0  ' Used to toggle between the two colors

    For R = 2 To LastRow
        ThisOrder = Cells(R, 1).Value
        PrvOrder = Cells(R - 1, 1).Value
        If ThisOrder <> PrvOrder Then Clr = 1 - Clr

        ' Select only the columns that are used
        Range("A" & R & ":M" & R).Select
        Selection.Interior.ColorIndex = RwColor(Clr)
    Next R
End Sub

ExcelTips is your source for cost-effective Microsoft Excel training. This tip (10517) applies to Microsoft Excel 97, 2000, 2002, and 2003. You can find a version of this tip for the ribbon interface of Excel (Excel 2007 and later) here: Changing Shading when a Column Value Changes.