Saving data upon clicked next and retrieve data upon clicked previous...

hi im having trouble with my page, i have a pop up listing that display all  the products available, so when a certain user selects a product it will just check provided on the left side of the screen, the problem here is only 30 items are displayed on the 1st page. and what if the user wants to select more than 30 so he will check all the checkboxes then click next so that the next 30 product will be displayed. my problem here is how im gonna save the previously selected items. please i really need your help .....


Thanks in advance,