Sail Number Wizard

The facility to enter sail numbers using the last 3 digits is a great option for the committee boat,
especially when classes are into 5/6 digit numbers.

The problem is that in order to use this facility, it is obviously vital to check for any
The only way we could do this was to export a competitor list to Excel, delete the unwanted digits
from each number, then sort the remaining numbers.

Fortunately, at this weekend's event, we only had 35 entries & there were no duplicates.
For a bigger entry this process would be a real pain.
Does anyone have an efficient solution for sorting numbers by the last x digits?