Number in Sequence Order

I have a application (VB – Oracle) used by 50+ users. Now for 1 module I have to generate Number in Sequence Order with the date saved and the no is displayed after the data is saved.

The number should not be duplicate in any of the rows.

I donot want to loss any no. from the sequence. How do I implement this code.

(e.g. LPO No., HelpDesk CASE ID etc….)

Thanks in advance.