Comparison with previous weeks orders query (and some calcs)

[PotatoDave]

I have a table that holds details of all provisional and actual orders. I need to then do a nunber of things with this data:
1) a percentage accuracy of the provisional vs Actual order (which I think I have done)
2) Create a production figure based on the provisional order and the accuracy of the previous weeks order on that day of the week for that product. (ie Prov order is 200, last week actual was 150% of Prov order so this week prod figure is 200x150%=300)
3) Compare the figure from No.2 with the actual order.
4) do some calculations of the figure from no.2 (ie 70% of it)

Table Structure is:
id (autonumber)
Product Code (text)
Order_Date (date)
Order_Time - AM/PM (text)
Order_Type - Prov/Act (text)
Order_Day - Day of Week (text) - calculated in form using vb
Delivery_Point - a/b (text)
qty (number)
concat - field that concatenates Date,Time,DelPoint (unique to each days order - but same for Actual or Prov order)

I have got the first one by having 2 queries (one for actual and one for provisional) and then in a third query matching these using the concat field and calculate the difference. This works ok but there may be a more elegant solution.

Many Thanks