Color cells based on cell value

Question

Can you help me what is wrong with my code. I get an error: Application defined or object defined error. I would like to color a cell based on a cell value. If a cell value equal to a cell-1 value the cell should be red. Error with this line: If Cells(i, 2).Value = Cells(i - 1, 3).Value Then

thank you

Sub colorcells()
ThisWorkbook.Worksheets("Sheet1").Activate
Range("A1").Select
    Dim i As Long
    lastrow = Cells(Rows.Count, "B").End(xlUp).Row
    For i = 1 To lastrow
        If Cells(i, 2).Value = Cells(i - 1, 3).Value Then
            Cells(i, 1).Interior.ColorIndex = 3
        End If
    Next i
End Sub 

Answer 1

Instead of using VBA, you can use conditional formatting if you are using Excel 2007 upwards, which is a lot easier to use. It provides you with dialog boxes which allow you to set rules.