Danke Dir, so hat es funktioniert:
 

Sub LinkBearbeiten()
'
' LinkBearbeiten Makro
'
'
Dim doc As Word.Document
    Dim hlk As Word.Hyperlink
    Dim strAddress As String
    Dim strSubAdress As String
    Dim zaehler As Integer
    Dim AText As String
    Dim PText As String
    Dim NewAdress As String
    Const such As String = "W-"
    
    Set doc = ActiveDocument
    
    For Each hlk In doc.Hyperlinks
        'Anzeigetext auslesen
        AText = hlk.TextToDisplay
        'Nur wenn Anzeigetext W- beinhaltet
        If InStr(AText, such) > 0 Then
            'Alte Adresse auslesen
            strAddress = hlk.Address
            'SubAdresse auslesen
            strSubAdress = hlk.SubAddress
            'Neue Adresse setzen
            NewAdress = strAddress & "?autoplay=o"
            hlk.Address = NewAdress
            zaehler = zaehler + 1
        End If
    Next hlk
    MsgBox (zaehler & " Hyperlinks bearbeitet")
End Sub