while ($myrow = mysql_fetch_array($result)) {
          $selected="";
          $id=$myrow["cod_morbi"];
          if ($cedula==$id || $_POST['cod_morbi']==$id) {
            $selected="selected";
            print "<OPTION value='".$myrow["cod_morbi"]."' $selected>".$myrow["morbi_d"]."</OPTION>";
 }