Duplicate Returns in Quarterly Query

[Ssnake57]

I am working on a data base on rental equipment. I have [Site], [Unit #], [Monthly Flow], [Month], [Start Date] & [Stop Date]. My Monthly Reports are working fine and the totals are accurate. My problem is when I try to do a Quarterly Query, I get duplicate numbers combining [Unit #] & [Site] due to the moving of equipment during the Quarter. I need to be able to stop a unit on one site and move to another while pulling the Sum of [Monthly Flow] for the Quarter from [Site]. Example:

Site Unit # Month Monthly Flow Start Date Stop Date
A 719 4-30-02 8955 4-2-02 5-20-02
B 815 4-25-02 7255 1-1-02 4-30-02
C 719 6-25-02 1055 6-2-02
D 815 5-25-02 6255 6-6-02


When I run a Quarterly Query I get

Site Unit # Month Qtrly. Flow
A 719 Q2 2002 10010
A 719 Q2 2002 10010
C 719 Q2 2002 10010
C 719 Q2 2002 10010
B 815 Q2 2002 13510
B 815 Q2 2002 13510
D 815 Q2 2002 13510
D 815 Q2 2002 13510

My Total for Qurter Should Show 23520 Instead I get 94080
Any Advice Would be appreciated Thanks.

Larry