Crystal report count record

How to do something like this?

Current year and series number

13-0001
13-0002
13-0003
13-0004
13-0005

my codes:

unbound field : "13-0001"

WHILEPRINTINGRECORDS;

LEFT({@UNBOUND},3) & TOTEXT(VAL(TRIM(RIGHT({@UNBOUND},4)))+1,"0000")