PL/SQL :: Insert Only Month And Year Instead Of Full Date

select b.penjara_id, p.penj_lokasi, a.no_daftar, b.episod, b.nama1,to_char(a.trkh_mula_prl,'dd/mm/yyyy') as trkh_mula_prl, to_char(bulan_proses,'mm/yyyy') as bulan_proses,
        b.epd, b.lpd
from prl_daftar_proses a, senarai_pesalah b, penjara p

where a.no_daftar=b.no_daftar
and a.episod=b.episod
and b.penjara_id = p.penjara_id
and a.setuju_jplp is null
and a.bulan_proses between to_date(:FROM,'dd/mm/yyyy') and to_date(:TO,'dd/mm/yyyy')
order by b.penjara_id, a.bulan_proses,a.no_daftarHi,

how i can insert only month and year from the value that have full date in the database?

for example,the date is 09/18/2012, but i just want to insert 09/2012 as parameter. If i want to insert only one parameter, i can do that..But i have problem when I want to insert two parameters..