Fixed...
instruccion = "SELECT * from tabla1 as t1 LEFT JOIN (SELECT * FROM " & "[MS Access;PWD=databasePWD;DATABASE=" & strpath & "].tabla1) as t2 ON t1.[TEL_NUM_FACTURA] = t2.[TEL_NUM_FACTURA] WHERE (((t2.TEL_NUM_FACTURA) Is Null))" Dim db As DAO.Database Dim rs As DAO.Recordset Set db = CurrentDb() Set rs = db.OpenRecordset(instruccion) rs.Close Set rs = Nothing