want to generate autonumber in specific format

[SKV]

I am creating a database and want to have primary key generated automatically in a specific format. Auto number serves the purpose but it generates only numbers.

I want the format to look something like "XYY###" where X stands for company codes, YY stands for year (09, 10....) and ### stands for 3 digits number.

Thanks in advance for the help

Regards
SKV