Consulta utilizando variáveis dentro do Between

Galera estou aqui mais uma vez, montei um select para gerar um relatório por período, tenho uma tela em php que utilizo para colocar as datas, "de" "até". Assim eu utilizo duas variáveis, $termo2 e $termo4. Meu select é bem grande com vários subs.e Dentro destes subs as datas precisar estár com estas variaveis. por exemplo: where nfe.data between '01-mai-2014' and '31-mai-2014'.

Como eu faria para adicionar as variáveis neste campo?

Abaixo o select completo.

select nf.dochd_own_ent_id, cl.entdf_dsc as cliente,
 nvl((select sum(it2.docsv_amt)
 from dochd nf2, docsv it2
 where nf2.dochd_iss_dt between '01-mai-2014' and '31-mai-2014'
 and nf.dochd_own_ent_id = nf2.dochd_own_ent_id
 and nf2.dochd_st = 91
 and nf2.dochd_doc_prc_tp = it2.docsv_doc_prc_tp
 and nf2.dochd_doc_prc_id = it2.docsv_doc_prc_id
 and ltrim(rtrim(it2.docsv_cd)) in ('AUR200','AUR001','01.02','01.01','01.03','301.03')),0) as Armazenagem,
 nvl((select sum(it2.docsv_amt)
 from dochd nf2, docsv it2
 where nf2.dochd_iss_dt between '01-mai-2014' and '31-mai-2014'
 and nf.dochd_own_ent_id = nf2.dochd_own_ent_id
 and nf2.dochd_st = 91
 and nf2.dochd_doc_prc_tp = it2.docsv_doc_prc_tp
 and nf2.dochd_doc_prc_id = it2.docsv_doc_prc_id
 and it2.docsv_cd in ('AUR002','02.02','02.01','02.03','302.03')),0) as Ger_risco,
 nvl((select sum(it2.docsv_amt)
 from dochd nf2, docsv it2
 where nf2.dochd_iss_dt between '01-mai-2014' and '31-mai-2014'
 and nf.dochd_own_ent_id = nf2.dochd_own_ent_id
 and nf2.dochd_st = 91
 and nf2.dochd_doc_prc_tp = it2.docsv_doc_prc_tp
 and nf2.dochd_doc_prc_id = it2.docsv_doc_prc_id
 and it2.docsv_cd in ('AUR094','07.01','07.04','03.01','03.11','03.02','03.04')),0) as Moviment,
 nvl((select sum(it2.docsv_amt)
 from dochd nf2, docsv it2
 where nf2.dochd_iss_dt between '01-mai-2014' and '31-mai-2014'
 and nf.dochd_own_ent_id = nf2.dochd_own_ent_id
 and nf2.dochd_st = 91
 and nf2.dochd_doc_prc_tp = it2.docsv_doc_prc_tp
 and nf2.dochd_doc_prc_id = it2.docsv_doc_prc_id
 and it2.docsv_cd in ('03.03','303.03','AUR029','03.13')),0) as uni_des,
 nvl((select sum(it2.docsv_amt)
 from dochd nf2, docsv it2
 where nf2.dochd_iss_dt between '01-mai-2014' and '31-mai-2014'
 and nf.dochd_own_ent_id = nf2.dochd_own_ent_id
 and nf2.dochd_st = 91
 and nf2.dochd_doc_prc_tp = it2.docsv_doc_prc_tp
 and nf2.dochd_doc_prc_id = it2.docsv_doc_prc_id
 and it2.docsv_cd in ('04.01','AUR004','04.03')),0) as Pesagem,
 nvl((select sum(it2.docsv_amt)
 from dochd nf2, docsv it2
 where nf2.dochd_iss_dt between '01-mai-2014' and '31-mai-2014'
 and nf.dochd_own_ent_id = nf2.dochd_own_ent_id
 and nf2.dochd_st = 91
 and nf2.dochd_doc_prc_tp = it2.docsv_doc_prc_tp
 and nf2.dochd_doc_prc_id = it2.docsv_doc_prc_id
 and it2.docsv_cd in ('05.03','05.02')),0) as averbacao,
 nvl((select sum(it2.docsv_amt)
 from dochd nf2, docsv it2
 where nf2.dochd_iss_dt between '01-mai-2014' and '31-mai-2014'
 and nf.dochd_own_ent_id = nf2.dochd_own_ent_id
 and nf2.dochd_st = 91
 and nf2.dochd_doc_prc_tp = it2.docsv_doc_prc_tp
 and nf2.dochd_doc_prc_id = it2.docsv_doc_prc_id
 and it2.docsv_cd not in ('AUR200','AUR001','01.02','01.01','01.03',
 '301.03','AUR002','02.02','02.01','02.03',
 '302.03','AUR094','07.01','07.04','03.01',
 '03.11','03.02','03.04','03.03','303.03',
 'AUR029','03.13','04.01','AUR004','04.03',
 '05.03','05.02')),0) as outros,
 sum(it.docsv_amt) total
 from dochd nf, docsv it, entdf cl
 where nf.dochd_iss_dt between '01-mai-2014' and '31-mai-2014'
 and nf.dochd_st = 91
 and nf.dochd_doc_prc_tp = it.docsv_doc_prc_tp
 and nf.dochd_doc_prc_id = it.docsv_doc_prc_id
 and nf.dochd_own_ent_id = cl.entdf_id

group by nf.dochd_own_ent_id, cl.entdf_dsc