Option Explicit
Private Sub Worksheet_SelectionChange(ByVal c As Range)
Dim plage As Range: Set plage = Range("a5:l34")
If c.Count > 1 Then Exit Sub
If Not Intersect(c, plage) Is Nothing Then
Select Case c.Interior.ColorIndex
Case xlNone: c.Interior.ColorIndex = 6
Case 6: c.Interior.ColorIndex = 3
Case 3: c.Interior.ColorIndex = 10
Case 10: c.Interior.ColorIndex = xlNone
End Select
Application.EnableEvents = False
c.Offset(, 1).Select
Application.EnableEvents = True
End If
End Sub