tabindex for formfields using Form Helper?

[eluser]5indies[/eluser]
i tried:

Code:

form_dropdown($fieldid,
                                isset($fieldargs['value'])?$fieldargs['value']:array('N/A'),
                                isset($fieldargs['selected'])?$fieldargs['selected']:'',
                                isset($fieldargs['js'])?$fieldargs['js']:'',"tabindex='10'");

bu it doesn't work.. tabindex parameter isn't included in the html