Private Sub Worksheet_Change(ByVal Target As Range)'Code by Sumit Bansal from https://trumpexcel.com
' To allow multiple selections in a Drop Down List in Excel (without repetition)
Dim Oldvalue As String
Dim Newvalue As String
Application.EnableEvents = True
On Error GoTo Exitsub
If Target.Address = "$I$2" Then
If Target.SpecialCells(xlCellTypeAllValidation) Is Nothing Then
GoTo Exitsub
Else: If Target.Value = "" Then GoTo Exitsub Else
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 & vbNewLine & Newvalue
Else:
Target.Value = Oldvalue
End If
End If
End If
End If
Application.EnableEvents = True
Exitsub:
Application.EnableEvents = True
End Sub