Yearly Data From Selected Range

Hi all,
I have the Following Query
It is working fine if the first month is 01 and Second month is 12
but i want like this if the user selects 200103 to 200203 i want the
value of composite should be added from 200103 to 200203 in one row
and other row from 200203 to 200303.
like this if the user selects from 200004 to 200304 i have to get 3 rows..
that is Yearly data..so how can i modify the following query or any new query.


select CONVERT(CHAR(4),period,112), sum(composite)
from cdh_price_gap
where CONVERT(CHAR(6),period,112) between '200101' and '200312'
group by CONVERT(CHAR(4),period,112)
order by CONVERT(CHAR(4),period,112)


Thanks