This isn't really a struts specific problem. I can think of two approaches:
1. Prepare your data as two collections, one for each table. Display your data as normal and have a radio button which corresponds to each row. When the >> button is clicked, the form is submitted and you have an appropriate action which moves the data associated the radio button to the other collection. Then forward/redirect back to your display
jsp (assuming you are using jsp).
2. Use javascript to alter the html of the page when the button is clicked.
The approach you take really depends upon whether you want to have a round trip to the server each time the button is clicked, whether the client is likely to have javascript enabled etc. etc. etc.