Private Sub Worksheet_Change(ByVal Target As Range)
Dim Oldvalue As Variant
Dim Newvalue As Variant
Application.EnableEvents = True
On Error GoTo Exitsub
If Not Intersect(Target, Range("C2")) Is Nothing Then
If Target.SpecialCells(xlCellTypeAllValidation) Is Nothing Then
GoTo Exitsub
Else
If Target.Value = "" Then GoTo Exitsub
Application.EnableEvents = False
Newvalue = Target.Value
Application.Undo
Oldvalue = Target.Value
If Oldvalue = "" Then
Target.Value = Newvalue
Else
If InStr(1, Oldvalue, Newvalue) = 0 Then
Target.Value = Oldvalue & "; " & Newvalue
Else
Target.Value = Oldvalue
End If
End If
End If
End If
Exitsub:
Application.EnableEvents = True
End Sub