Bit of a though request from boss, and did not want to say "Dunno how"

Each time a new product are added I must assign it a product code, which will be a 3 digit numerical code.
For the first 9 products it should be "010" to "090".
After that it should be "110" to "190", then "210" to "290", etc.

Anyone did sth like this. Bit late for me to think straight.