Help With The Selection

SELECT Distinct a.group_code, a.group_name + '-'+ a.group_note As full_name ,
b.station_nbr, b.beg_eff_date, b.end_eff_date,
Round( e.C02_pct,3)As C02_pct, MAX( e.sample_date)As Highest_Sample_Date, d.station_name
from [HOU-TIES01].TIES_Gathering.dbo.group_detail a
Inner Join [HOU-TIES01].TIES_Gathering.dbo.station_group b on a.group_code = b.group_code
Inner Join [HOU-TIES01].TIES_Gathering.dbo.station_type c on b.station_nbr = c.station_nbr
Inner JOIN [HOU-TIES01].TIES_Gathering.dbo.station d ON c.station_nbr = d.station_nbr
Inner JOIN [HOU-TIES01].TIES_Gathering.dbo.gas_analysis e ON d.station_nbr = e.station_nbr
Where (b.station_nbr=e.station_nbr)and (b.group_code = a.group_code) and
(a.group_type = 'NPN')and( b.end_eff_date >=DATEADD(mm,DATEDIFF(mm,0,dateadd(mm,-0-datepart(day,0),getdate())),0))
and ( (c.type_code = 'WHM')or ( c.type_code = 'CRP'))and
(e.sample_date Between DATEADD(mm,DATEDIFF(mm,0,dateadd(mm,-0-datepart(day,0),getdate())),0)
and DATEADD(mm, DATEDIFF(mm,0,getdate()), 0))
and e.seq_nbr =
(select max(x.seq_nbr)
From [HOU-TIES01].TIES_Gathering.dbo.gas_analysis x
Where x.station_nbr = b.station_nbr
and x.sample_date= e.sample_date )
and e.C02_pct =
(Select max(x.C02_pct)
From [HOU-TIES01].TIES_Gathering.dbo.gas_analysis x
Where x.station_nbr = b.station_nbr
and x.sample_date= e.sample_date )
Group by a.group_code, a.group_name, a.group_note, b.station_nbr, b.beg_eff_date, b.end_eff_date, e.c02_pct, d.station_name
order by a.group_code



ok. Here is how the data looks.
Group
code station_nbr beg_eff_date end_eff_date C02 sample_date
0004 D01G000819 2007-09-01 3000-12-31 0.40 2007-10-02
0004 D01G000819 2007-09-01 3000-12-31 2.49 2007-10-09


What I am trying to do is to select the most current sample date. In this case "2007/10/09" when station_nbr and group_code are the same for both dates.

Thank You for all your help!!!!
From the Jr.in SQL