[TYPO3] File link (simple question?)

[Tony P]

I'm trying to re-purpose a field in the si_bibtex extension to make it 
appear as a link to an uploaded file.

I've got it working in the back end by adding this to extTables.php:

$GLOBALS['TCA']["tx_sibibtex_entries"]['columns']['institution']['config']['type'] 
= 'input';
$GLOBALS['TCA']["tx_sibibtex_entries"]['columns']['institution']['config']['wizards'] 
= array(
    'link' => Array(
       'type' => 'popup',
       'title' => 'Link',
       'icon' => 'link_popup.gif',
       'script' => 'browse_links.php?mode=wizard',
       'JSopenParams' => 
'height=300,width=500,status=0,menubar=0,scrollbars=1'
       )
);

However on the page in the front end, it just appears as plain text, eg

fileadmin/user_upload/whitepaper.pdf

How do i get it to render as a link to the file, and with the link text 
being just the filename, eg

[a href="fileadmin/user_upload/whitepaper.pdf"]whitepaper.pdf[/a]

I hope someone can help me.