How do i create a custom primary key?

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VB

Good Day to all,

Please help me with my project, I would like to create a Custom Primary Key in my database design,
the format is [current year][current month][3 digit counter].
This goes something like this ==> 201602001. Next id should be 201602002 and so on, but here is the catch, the following month it should display ==> 201603001 then next id should be 201603002 and so on. The three digit counter should reset to 001 every month.

Is this possible?

Thank you in advance....

What I have tried:

I am new to programming and with my limited knowledge I was in the dead end. I consider creating another table to create that desired format but it would be a redundancy to the existing pk. Thank you