Removing Duplicates from an invoice table

Hello Guys & Girls,

I am new to these forums & they are quiet helpful so far

I have a system setup in Excel that allows my workers to enter data into a spreadsheet and with this I run the invoice system from that gathered information. The issues I am having is that each time my workers visit a location & they enter it in my sheet the invoice copy's exactly how the main sheet is.

(So if they go to Location 1 3x then it'll be as follows

Location 1 5/12/2013 400 Gallons
Location 1 5/13/2013 100 Gallons
Location 1 5/16/2013 600 Gallons

I want to make the main page that the boys enter their data into have multiple entries but when I print the invoices at the end of the month I would like the multiple entries to be grouped and added together to form 1 entry and a total of the chemical delivered to site.

I have currently just added more sheets for the areas that we service I have not looked into running a separate file for just invoices at this stage but I am interested in doing so or if I need to to make this work.

I have attached an image of the 'other' crap that we have between "Location 1" "Date Of Arrival" "Due Date" "Name" "Parts etc" "Gallons"

We have 4 Areas that divide our locations up.

so basically its.

Location 1 \
Location 2 - AREA 1
Location 3 /

Location 4 \
Location 5
Location 6 - AREA 2
Location 7 /

Location 8 - AREA 3
Location 9