[BucShot]

However , the " who's online " page shows " unknown location when someone is trading on my forum

This is a pretty simple fix. Edit functions_online.php (includes directory)
Find

case 'gallery':
			$userinfo['action'] = $vbphrase['viewing_gallery'];
			break;

Add below

case 'vbtrade':
			$userinfo['action'] = $vbphrase['viewing_stock_trader'];
			break;

Then find

case 'gallery.php':
		$userinfo['activity'] = 'gallery';
		break;

Add below

case 'vbtrade.php':
		$userinfo['activity'] = 'vbtrade';
		break;

Next go to your Phrase Manager and add a phrase.
Phrase Type: Who's Online
Product: vBulletin
Varname: viewing_stock_trader
Text: Viewing Stock Trader

Save it and your Who's Online should now show Viewing Stock Trader.