Private Sub Document_ContentControlOnExit(ByVal CC As ContentControl, Cancel As Boolean)

Dim Text As String
Dim Empty As String
Text = vbCrLf & "Some new Text: " & vbCrLf
Empty = " "

    Select Case CC.Tag
    Case Is = "Tagname"
        Select Case CC.Range.Text
            Case Is = "Hi"
                Call ChangeText(Empty)
            Case Is = "Hello"
                Call ChangeText(Text)
            Case Is = "Welcome"
                Call ???
        End Select
    End Select

End Sub

Sub ChangeText(ByVal Text As String)
Application.ScreenUpdating = False

    Selection.GoTo What:=wdGoToBookmark, Name:="TestBookMark"
    Selection.Delete Unit:=wdCharacter, Count:=1
    Selection.InsertAfter Text
     
    ActiveDocument.Bookmarks.Add Range:=Selection.Range, _
       Name:="TestBookMark"
    Selection.Collapse

Application.ScreenUpdating = True
End Sub