One thing I noticed was you closed the recordset and destroyed the recordset in the main code. If an error occurs it will skip over these lines to the error handler then exit out. Wouldn't these lines be better in the DoExit area just before Exit Function?

doExit:
    HandleDroppedFile = DocumentID
    If Not rs Is Nothing Then rs.Close
    Set frm = Nothing
    Set rs = Nothing
    Exit Function