Concatenate validation lists to same sheet.

Hello.

I have used this code before to combine two validation lists.

Hopefully, this will be easy. Now, instead of putting the combined list on a separate sheet, I'd like it in the Z column of the "Lists" sheet (the sheet the separate lists are on.). And instead of a button, some kind of way where if I add/remove entries to either of the separate lists ("VendCity" and "CustComb"), the combined list ("MyBigList") automatically grows and shrinks so it is always accurate.

Here's the code:

Private Sub CommandButton2_Click()
Dim wsBigList As Worksheet, ws As Worksheet
    Dim wsBigListFound As Boolean: wsBigListFound = False
    For Each ws In ActiveWorkbook.Sheets
        If ws.Name = "Big Combined List" Then
            Set wsBigList = ws
            wsBigListFound = True
            Exit For
        End If
    Next ws
    
    If wsBigListFound = False Then
        Set wsBigList = Sheets.Add(after:=Sheets(Sheets.Count))
        wsBigList.Name = "Big Combined List"
        wsBigList.Visible = xlSheetHidden
    End If
    
    With wsBigList
            .Columns(1).Clear ' Clear MyBigList ready for copy/paste
            Sheets("Lists").Range("Plant").Copy .Range("A1")  'Copy 1st dynamic range and paste to A1 of Sheet4
            Sheets("Lists").Range("Shop").Copy .Cells(.Rows.Count, "A").End(xlUp)(2, 1)  'Copy 2nd dynamic range and paste to 1 below last used row of Sheet4
            .Range("A1", .Cells(.Rows.Count, "A").End(xlUp)).Name = "MyBigList" 'Name the new dynamic range
    End With
End Sub

Any ideas?

Respectfully,

Lost