Loop in VBA code

Public Sub FunWithLoop()
    Dim rng As Range
    Dim cel As Range
    ' Speed up execution by not updating the screen
    Application.ScreenUpdating = False
    ' Determine the used range in column A
    Set rng = Range(Range("A1"), Range("A" & Rows.Count).End(xlUp))
    ' Remove the fill color
    rng.Interior.ColorIndex = xlColorIndexNone
    ' Loop through the cells of the range
    For Each cel In rng
        ' First check whether the value is greater then 20
        If cel.Value > 20 Then
            ' If so, color the cell blue
            cel.Interior.Color = vbBlue
        ' Else, check whether the value is greater than 10
        ElseIf cel.Value > 10 Then
            ' If so, color the cell red
            cel.Interior.Color = vbRed
        End If
    Next cel
    ' We're done, now show the result
    Application.ScreenUpdating = True
End Sub

Excel