Numbering starts over when part of the name changes

[huviline]

Hello!
Is it possible to add alphabet (a-z) suffix but it should start over when a certain 4 digits changes.

Names before:
12345_UA_6677
12346_UA_6677
12347_UA_1025
12348_UA_1025
12349_UA_1025
12350_UA_7456

Names I need (add suffix _aa-_zz but it should start over when the 4 digits change in the end of the origin name):
12345_UA_6677_aa
12346_UA_6677_ab
12347_UA_1025_aa
12348_UA_1025_ab
12349_UA_1025_ac
12350_UA_7456_aa

[Admin]

Try using Break - Reset the auto-number when the nnn character changes. e.g. enter 4 to cause the number to reset when the 4th character of the NEW name changes.

[huviline]

Seems like the first numbers confuse the "break". If I loose them then it seems to work, but I need the first numbers also
Nevertheless, thank you, I will think forward how to add first numbers back!