automatic number generator for module pool programmes while saving

Hi all,

While doing module pool Programming, After completion of data entered into screen fields, while saving it should generate automatic serial number in an ascending order.

Right now i am following this logic.

fetch the data from database and sort in descending order and increase one number and populate in to that particular field . Then i am showing sucessfull message that order has created with serial number has created.

<b>For this functionality any function module is available in sap. if available please let me know..</b>

Thanks in avance.

praveen