bsstaveley 0 Newbie Poster

I am trying to create a quotation form where clients can choose a product series number from a drop down menu ie 2000 series, 4000 series ect then a product number from that series from another drop down menu ie 2450, 2570. Once they have selected a product number i then need a series of checkboxs to appear below where a client can choose accessories for that particular product number. How is the best way of doing this and does someone have a script wriien for this as i am a beginner!!!