how to auto create a PurchaseOrder Num based on date + count

how to auto create a PurchaseOrder Num based on date + count

Dear all,

HI! HOw are you? In my event registration form, I would like to auto create a 9 digit purchase order based on the following idea

(1) option #1: date + serial counter
if today's date is 2008/10/25 when the user register the event, then the PO number will be 081025001 (where 081025 is the date, and 001 is the serial counter)
- the challenge is that I don't know how to
(1) how to change date into a requested format
(2) how to create a serial counter where the counter will stores the number of registration

(2) option #2: date with time
if today's date is 2008/10/25 10:35 then the PO number will be 102510350 (where 1025 is Oct 25 and 1035 is 10:35, 0 will just a dummy number added)
- the challenge is that I don't know how to
(1) how to change the date and tim into the request format

If you have any idea or past example, please kindly help! Really appreciate the community support!

Creator is a really good tool! I am learning as I go!

David