Adding Field to Add Content

I've spent the last couple days browsing the forum and I can't seem to find an answer to my question. What I am trying to do is add a new field to node/add/story, store that into a new table in the database, and then use those values elsewhere on my site. Currently I figured out how to add the field using hook_form_alter.

function ftb_rtstocks_form_alter($form_id, &$form) {
switch ($form_id)
	{
	case 'story_node_form':
		$options = array(0 => t('Unrated'), 1, 2, 3, 4, 5);
		
		$form['ftb_rtstocks'] = array(
			'#type' => 'fieldset',
			'#title' => t('Stocks')
			);
		
		$form['ftb_rtstocks']['symbols'] = array(
			'#type' => 'textfield',
			'#title' => t('Symbols'),
			'#description' => t('Enter a stock symbol.')
			);
			
		$form['ftb_rtstocks']['#weight'] = -1;
	}
}

and I figured out how to use the info in my database using hook_nodeapi()

function ftb_rtstocks_nodeapi(&$node, $op, $teaser, $page) {
switch ($op)
	{
	case 'update':
		case 'insert':
		ftb_rtstocks_node_save($node->nid, $node->ftb_rtstocks);
		break;
	case 'insert':
		ftb_rtstocks_node_save($node->nid, $node->ftb_rtstocks);
		break;
	
	case 'view':
		$types_to_ftb_rtstocks = variable_get('ftb_rtstocks_nodetypes', array('story'));
		if (!in_array($node->type, $types_to_ftb_rtstocks))
			{
			break;
			}
		
		// Get previously saved symbols.
		$result = db_query("SELECT symbols FROM {ftb_rtstocks} WHERE nid = %d", $node->nid);
		$node->ftb_rtstocks = db_result($result);
		
		// Add stock ticker as a content item.
		$node->content['ftb_rtstocks_ticker'] = array('#value' => theme('nodeapi_ftb_rtstocks', $node->ftb_rtstocks), '#weight' => 10, );
	}
}

However I can't figure out how to write my "symbols" field into the database. Right now I have:

function ftb_rtstocks_node_save($nid, $form_values) {
$symbols = $form_values['symbols'];

db_query("DELETE FROM {ftb_rtstocks} WHERE nid = %d", $nid);
db_query("INSERT INTO {ftb_rtstocks} (nid, symbols) VALUES (%d, '%s')", $nid, $symbols);

drupal_set_message(var_dump($form_values));
}

....but that only writes the nid and not the "symbols" field from my form that I am inserting into node/add/story.

Thanks for your ideas to point me in the right direction!