VBA creer une macro

Private Sub Worksheet_Change(ByVal Target As Range)
    If Target.Column <> 3 Then Exit Sub
    If Target = "" Then Exit Sub
    If Target < 0 Then Target.Interior.Color = RGB(255, 0, 0)
    If Target = 0 Then Target.Interior.Color = RGB(20, 255, 210)
    If Target > 0 Then Target.Interior.Color = RGB(0, 255, 0)
End Sub

Option Explicit
Sub Couleur_selon_valeur()
    Dim i As Long
    Application.ScreenUpdating = False
    For i = Cells(Rows.Count, "a").End(xlUp).Row To 2 Step -1
        With Range("c" & i)
            .FormulaR1C1 = "=RC[-1]-RC[-2]"
            If .Value < 0 Then .Interior.ColorIndex = 3
            If .Value > 0 Then .Interior.ColorIndex = 43
            If .Value = 0 Then .Interior.ColorIndex = 4
        End With
    Next i
    Application.ScreenUpdating = True
End Sub

Private Sub Worksheet_Change(ByVal Target As Range)
    If Not Intersect(Target, [c1:c100]) Is Nothing And Target.Count = 1 Then
        Select Case Target.Value
        Case Is < 0
            Target.Interior.ColorIndex = 3
        Case Is = 0
            Target.Interior.ColorIndex = 4
        Case Is > 0
            Target.Interior.ColorIndex = 35
        Case Else
            Target.Interior.ColorIndex = xlNone
        End Select
    End If
End Sub

Option Explicit
Sub Couleur_selon_valeur_V2()
    Dim c As Range
    Application.ScreenUpdating = False
    For Each c In Union(Range("a2", Cells(Rows.Count, "a").End(xlUp)), Range("f2", Cells(Rows.Count, "f").End(xlUp)))
        With c.Offset(, 2)
            .FormulaR1C1 = "=RC[-1]-RC[-2]"
            If .Value < 0 Then .Interior.ColorIndex = 3
            If .Value > 0 Then .Interior.ColorIndex = 43
            If .Value = 0 Then .Interior.ColorIndex = 4
        End With
    Next c
    Application.ScreenUpdating = True
End Sub

Option Explicit
Sub Couleur_selon_valeur_V3()
    Dim c As Range
    Application.ScreenUpdating = False
    For Each c In Union(Range("a2", Cells(Rows.Count, "a").End(xlUp)), Range("f2", Cells(Rows.Count, "f").End(xlUp))).SpecialCells(xlCellTypeConstants, 23)
        With c.Offset(, 2)
            .FormulaR1C1 = "=RC[-1]-RC[-2]"
            If .Value < 0 Then .Interior.ColorIndex = 3
            If .Value > 0 Then .Interior.ColorIndex = 43
            If .Value = 0 Then .Interior.ColorIndex = 4
        End With
    Next c
    Application.ScreenUpdating = True
End Sub