Target.address for multiple rows in Excel - excel

Question

I need to reference an entire column of Excel spreadsheet, with a drop-down list using VBA. The code i got online works only for a single cell which is "$M$2". How can i define a range for the entire column?
Private Sub Worksheet_Change(ByVal Target As Range)
' To Select Multiple Items from a Drop Down List in Excel
Dim Oldvalue As String
Dim Newvalue As String
On Error GoTo Exitsub
If Target.Address = "$M$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
Target.Value = Oldvalue & ", " & Newvalue
End If
End If
End If
Application.EnableEvents = True
Exitsub:
Application.EnableEvents = True
End Sub

Answer 1

Firstly, Target may be a single cell or multiple cells, depending on what the user changed
To test if any cell in (and only in) column M changed, use
If Target.EntireColumn.Address = "$M:$M" Then
To test if any cell in Target is in column M use
Dim rng As Range
Set rng = Application.Intersect(Target, Me.Columns("M"))
If Not rng Is Nothing Then
Note: the rest of your code will need to be modified to allow for Target being more than one cell