Max Record Count And Date Range

I am currently using this SQL code to capture some records over the last 2 months and it has been working great. I am now being asked if I can change this code with specifications:

1) Scan the records in the system until the count (*) as Volume reaches 30 because they prefer that as a denominator when figuring an average

2) Only run the scan for a maximum of 6 months.

So, there will most likely be some records that do not reach a volume number of 30 in this date range. In this instance we will just take the maximum volume number reached at 6 months.

So, how can I write this so it will build the file each time a record has reached the maximum of 30 and keep scanning back until we reach 6 months? If someone could lead me in the right direction on the proper order of the methodology in my code to accomplish these results it would be greatly appreciated. Desperate!

declare
@startdate smalldatetime,
@enddate smalldatetime ,
@month int,
@year int

select
@startdate = dateadd (mm, -2, getdate())
SELECT
@month = datepart (month, @startdate),
@year = datepart (year, @startdate)
SELECT
@startdate = convert (smalldatetime, convert(varchar(2), @month) + "/1/" + convert (varchar(4), @year))

select
@enddate = dateadd (mm, 2 , @startdate)

select distinct

pe1.patev_loc_id as LocID,
pp_cproc_id_r as ProcID,
count (*) as Volume,
sum (datediff (mi, pe1.patev_event_time, pe2.patev_event_time)) as Minutes,
sum (datediff (mi, pe1.patev_event_time, pe2.patev_event_time))/count(*) as AvgMin

from
risdb_rch08_stag..performed_procedure (index pp_serv_time_r_ndx),
risdb_rch04_stag..patient_event pe1,
risdb_rch04_stag..patient_event pe2

where
pp_service_time_r between @Startdate and @Enddate
and pp_asn_req_no = pe1.patev_asn_req_no
and pp_asn_seq_no = pe1.patev_asn_seq_no
and pp_status_v = 'CP'
and pp_rep_id > 0
and pe1.patev_event_code = 'PB'
and (pp_asn_req_no = pe2.patev_asn_req_no
and pp_asn_seq_no = pe2.patev_asn_seq_no
and pe2.patev_event_code = 'PL')
and datediff (mi, pe1.patev_event_time, pe2.patev_event_time) > 0

group by
pe1.patev_loc_id , pp_cproc_id_r