different Autonumeric field

I need an autonumeric like 000-0000-0001, 000-0000-0002 and growing after 1000 order, it gets to 000-0001-0000.

Ill also need an autonumeric like this aaa-0001, aaa-0002, bbb-0001

any idea how to do this in access or should I have to make it all by code, using len , left and right functions???
thanks for your help,

Cybersandokan

You may use AutoNumber in Access so you can at least get unic number, however you will need to write your own logic to creat that pattern and then store in the another field (if you have to).