How can i dynamically add value to the auto increment field?

You can't add your own value to an autoincrement database field - the whole idea is that it is allocated and maintained by the database. Any attempt to write a value to an autoincrement field will throw an exception instead of the insert or update operation being performed. The reason is simple: you do not know what the next available field is, and neither does the database until the insert operation is performed to create the new record. You may think you do, but remember that databases are generally multiuser and another user can easily write his record(s) while you are getting yours ready...