checkbox question

Hi I was wondering how I could do this. I have a from for companies to fill out, in the from, there are 9 checkboxes for regions eg. National etc etc Whenthose are selected, the values are inserted in the db (if they are not selected, a blank is inserted ) Now when people search for companies, they have a similar form. The problem is that when someone selects regions, and some of the checkboxes are not selected, even the blank references will be picked up ( as the search form checkboxes have been left unselected) How could get around this ? i was thining of replacing the blanks with a .. or something when companies are added to the db and certain areas are not selected. Could this work ? and if so how could I do that ? thanks Gianni