Trying to add a subject to the tellafriend page - Please Advise

Hi,

I'm trying to add a subject field to the tellafriend page. I'm able to insert the following code and get it to show up on the form, but how to I get it to render in the email that is sent as the subject?


$form['tellafriend_subject'] = array(
'#type' => 'textfield',
'#title' => t("Subject"),
'#size' => 70,
'#maxlength' => 255,
'#required' => TRUE,
'#description' => t(''),
);


Any advice would be appreciated,

CarbonPig