There is no need to change the path. Simply tell the macro where to save the document. The following will save the file in the appropriate place regardless of the current save location.
Code:
Private Sub CommandButton3_Click()
Dim dtToday As String
Dim sPath As String
sPath = Options.DefaultFilePath(wdDocumentsPath) & "\"
dtToday = Format(Date, "ddmmyyyy")
ActiveDocument.SaveAs2 sPath & "Waiver_" & dtToday & ".docx"
End Sub