Row Colours In Report

I got the following code from:-

http://www.microsoft-accesssolutions.co.uk/alternate_row_colours.htm

This is to give me alternating row colours in report detail section but cannot make it work.
Please could someone tell me where I am going wrong?
Not sure where to put the bit "Private m_RowCount As Long"
The Rest apparently goes in the report detail section OnFormat event.

Private m_RowCount As Long

Private Sub Detail_Format(Cancel As Integer, FormatCount As Integer)
m_RowCount = m_RowCount + 1
If m_RowCount / 2 = CLng(m_RowCount / 2) Then
Me.Detail.BackColor = 15263976 'Change value to the color you desire
Else
Me.Detail.BackColor = 14811135 'Change value to the color you desire
End If
End Sub

Thank you Guys and Gals.