Excel - 多项选择下拉列表 - 不重复选择

我在 Excel 电子表格上开发了可以使用以下代码在下拉列表中选择多个项目的方法：

Private Sub Worksheet_Change(ByVal Target As Range)

Dim rngDV As Range
Dim oldVal As String
Dim newVal As String
If Target.Count > 1 Then GoTo exitHandler

On Error Resume Next
Set rngDV = Cells.SpecialCells(xlCellTypeAllValidation)
On Error GoTo exitHandler

If rngDV Is Nothing Then GoTo exitHandler

If Intersect(Target, rngDV) Is Nothing Then

Else
  Application.EnableEvents = False
  newVal = Target.Value
  Application.Undo
  oldVal = Target.Value
  Target.Value = newVal
    If oldVal = "" Then

      Else
      If newVal = "" Then

      Else
      Target.Value = oldVal _
        & ", " & newVal

      End If
    End If
End If


exitHandler:
  Application.EnableEvents = True
End Sub

但是，我现在想验证下拉列表项只能选择一次的答案。优选地，如果用户再次选择该项目，则将其删除。

任何帮助将不胜感激。

尝试这个：

Private Sub Worksheet_Change(ByVal Target As Range)
    Const SEP As String = ", "
    Dim rngDV As Range
    Dim oldVal As String
    Dim newVal As String
    Dim arr, m, v
    If Target.Count > 1 Then GoTo exitHandler

    On Error Resume Next
    Set rngDV = Target.SpecialCells(xlCellTypeSameValidation)
    On Error GoTo exitHandler
    If rngDV Is Nothing Then Exit Sub
    
    newVal = Target.Value
    If Len(newVal) = 0 Then Exit Sub 'user has cleared the cell...
    
    Application.EnableEvents = False
    
    Application.Undo
    oldVal = Target.Value
    
    If oldVal <> "" Then
        arr = Split(oldVal, SEP)
        m = Application.Match(newVal, arr, 0)
        If IsError(m) Then
            newVal = oldVal & SEP & newVal
        Else
            arr(m - 1) = ""
            newVal = ""
            For Each v In arr
                If Len(v) > 0 Then newVal = newVal & IIf(Len(newVal) > 0, SEP, "") & v
            Next v
        End If
        Target.Value = newVal
    Else
        Target.Value = newVal 'EDIT
    End If

exitHandler:
      Application.EnableEvents = True
End Sub