Weighted Averages In A Query

I have developed the following query to summarise a blast design at a mine site.

Pattern Depth m Subdrill Burden Spacing BCM/hole #Holes BCM
1.00 7.00 1.00 3.00 3.00 54 10 540
1.00 7.00 1.00 3.50 3.00 63 10 630
2.00 7.00 1.00 3.50 3.00 63 10 630
2.00 7.00 1.00 4.00 3.00 72 10 720

Now there will be many patterns, the above however only contains one (called 1). Now what i need is the average Depth, Subdrill, Burden, Spacing, bcm/h. In MS Excel I would have following:

Average BCM per hole = Sum of BCM / Sum of Holes

How to do this in Access? Then just to make it more difficult I want to have the average BCM for each different pattern.