[Zope] how to presev information

Hi, I'm a new zope programmer. I created a page which show different products (from a oracle database) which can be selected (products are shoiwn in checkbox format). As I have a lot of product I also manage button ('Next' and 'previous') The proble is : When I select some products from on page and then I use the button 'next' or 'pervious I lose the selected product of the last page.. Is someone can help me and give me some solution ?? Thanks for your help