javascript - checkbox

Hello, I need javascript for my custom form: ------------------------ I have 3 checkbox Cb1 Cb2 Cb3 (disabled – can’t select) I want when user check cb1, it’ll add 10 to total form. Cb3 still disabled. When user check cb2, it’ll add 15 to total form and cb3 is enable. If they uncheck cb2, cb3 is disable and total is not set value of cb2, cb3. If user check cb3, it’ll add 50 to total form. I want total form will auto show value like this page: [login to view URL] ------------------------ Please provide demo. I'll budget max $5 Thank you.