Hi,
Off the top of my head, I think you could just hide the third right hand column by using an 'if' statement. To remove the column on the checkout page add the 'if' statement above the opening <td> tags for the column:
Code:
{if $main ne "checkout" }
and then after the closing </td> tags of that column:
You can replace the "checkout" with the name of the smarty variable for any other pages where you wish to hide the right hand column.
HTH