I want to create a billing software in which the bill information stored in table having column
bill_no,date, buyers name ,amount

when i click the any column of the database it open another table (may be like nested table) which contains all items with their details displayed in bill

if it require any code than please write in the post

The first thing to do is design the database. What database engine do you want to use? MySQL, MS-Access, Orical, ... there are dozens of them. Do you know SQL? If not then you will have to study/practice it. There are lots of books on amazon.com that help you with that. Use google and you might even find free "sql tutorials".

Once the above is done, you need to take pencil & paper in hand and design the layout of the screens and write down what each of the buttons, list boxes and check boxes will do. This will give you a clear understanding of what your program will do and what functions you need to write.

Once all the above is completed you can begin coding. If you try to code beforehand you will wind up recoding stuff that doesn't work and wasting a lot of your time. You can still make a few design changes after you start coding, but that will probably not happen often, if at all.