Shading alternate groups, not rows?

[A-Reading]

I'm sorry to join and then immediately ask questions, but I'm in a bit of a fix and have been able to find almost nothing pertaining to my situation online.
It is very easy to make Excel automatically colour every other row. But I need to colour every other group. My workplace has a standard procedure for certain kinds of spreadsheets: We gather the relevant data from our database (names, organizations, etc.), and then sort them according to organization. Then, we manually shade every other group of rows that belong to that organization. So, for instance, if there are six organizations, we would sort them and then shade organizations 2, 4 and 6. Now, these groups are rarely the same size, so I cannot just get Excel to shade every other group of three rows. Organization 1 may have four entries, and Organization 2 may have only one, for instance. So, the first four rows would not be shaded, but then the next one would be. Then however many entries Organization 3 has would be shaded, et cetera. It would save us a great deal of time, in the long run, if we could get excel to automatically alternate shading by group, but I can find little advise on how to do that. Is it really possible?

[MickG]

Try this:-

Sub MG22May03
Dim Rng         As Range
Dim Dn          As Range
Dim Temp        As String
Dim col         As Integer
Dim fd          As Boolean
Set Rng = Range(Range("A1"), Range("A" & Rows.Count).End(xlUp))
Temp = Rng(1)
For Each Dn In Rng
    If Not Temp = Dn Then
        fd = fd Xor True
        col = IIf(fd, 34, xlNone)
    End If
Dn.Offset(, 2).EntireRow.Interior.ColorIndex = col
Temp = Dn
Next Dn
End Sub

Regards Mick