Sub Worksheet_SelectionChange
On Error GoTo Fin
If Target.Count > 1 Then Exit Sub
If Not Intersect(Target, Range("E3:E34,K3:K34,E38:E69,K3:K69,E73:E104,K73:K104")) Is Nothing Then
If Cells(Target.Row, Target.Column - 1) <> "" And _
Cells(Target.Row, Target.Column - 2) <> "" And _
Cells(Target.Row, Target.Column - 3) <> "" Then
If Target = "X" Then
Target = ""
Cells(Target.Row, Target.Column - 1).Select
Else
Target = "X"
Cells(Target.Row, Target.Column - 1).Select
End If
End If
End If
Fin:
End Sub