[ic] Preorder problem

[Jon]

I have the below link to allow a person to Preorder an item that is out
of stock.
This works fine unless the person visits the out of stock pre-order page
for the same
item multiple times. If they do that then they end up with multiple
basket rows
of the same number as opposed to a single basket entry with multiple
quantity.

<a href="[area href=order arg="[scratch code]"]">Click Here To
Preorder</a>

After clicking the above link the user is taken to cart/order.html,
which I know
doesn't exist per se, but what code do I need to tweak to create a
solution
for this problem ??

Jon