Automatic reference based on year and incremental value

Hi all

I would like to automatically allocate a reference to projects in the following format

financial year & " - " & incremental number starting at 1001 (where the incremental value resets when we start a new financial year)

eg.
2020 - 1001
2020 - 1002
2020 - 1003
2021 - 1001
2021 - 1002

any ideas how I might go about this?