They maybe more to it than this I will check for you if it does not work but I think it could:
In skin1/main/orders_list.tpl
Code:
<td style="text-align: center;"><a href="orders.php?username={$orders[oid].login}" title="View orders from this client">{$orders[oid].total_orders}</a></td>
You will need to add a header column etc to match or all your columns will be out. Give it a try and let me know if you need more help with it.
Rob