You would have to own eCart to do it....
1) Create a new Shopping Cart called Wish List
2) Place "Add to Wish List" buttons on the product pages just like the add to cart buttons
3) You would have to require people to log in before seeing the "Add to Wish List" button
4) Create a view wish list page displaying your wish list cart
5) Create a database table to store the wish list items... it could contain just an autonumber column, the productid, userid, quantity, and the options (if you are using options)
6) Apply the Store Cart Details In Database server behavior on the wish list page so that the database stays current
7) Apply the Add to Cart from Database server behavior to repopulate the wish list cart on the login page
8) Place add to cart buttons in your wish list to transfer items from the wish list to the actual cart
Lots of steps... the final two are probably the most difficult, but very doable.
If you want help, this is something we can definitely help with in a premier support ticket.