Ads Manager - manual feature ad

We run a site with ads manager Joomla 1.5 native. We tried a lots of module made for featured ads, but they had a lots of bugs. We need a small customization in the ads manager. We want to set up the featured ads manually, and display it in a module. No category restrictions. How we want it? In the adminsitration page, under Adsmanager / ADs section there is a list with all the ads, we just simple want a checkbox or tick here in a new column that is it featured or not. Than the administrators just have to scheck in the ads they want to promote. The module The module shows 12 lines of featured ads, if there is more, it randomly fills it with the featured ads. It is in list stlye ( <li> )