[razortw]

Hello.
This can be done by just editing Smarty templates.
Basically, you will need to find the template that is responsible for displaying the part of the page you want to change, and wrap your block into a condition like this
{if $main eq 'catalog' and $cat eq %your_category_id%}
code of your block
{end}
That is it.
Let me know if this helps.