Averaging sub categories from the bottom up

[erikpendragon]

How can i average each lower level sub group and put its value in its upper level. ex

Average all the numbers in E that are a 4 and place the result above in the 3 spot.
Average all the numbers in E that are a 5 and place the result above in the 3 spot.
Average all the numbers in E that are a 7 and place the result above in the 6 spot.
Average all the numbers in E that are a 8 and place the result above in the 6 spot.
Average all the numbers in E that are a 3 and place the result above in the 2 spot.
Average all the numbers in E that are a 6 and place the result above in the 2 spot.
Average all the numbers in E that are a 2 and place the result above in the 1 spot.

i can do this manually
=IFERROR(ROUND(AVERAGE(G6:G9),0),"")
=IFERROR(ROUND(AVERAGE(G5,G10),0),"")
but this doenst update properly if i add a new task.
How can i set this up to do it automaticly.

A	B	C	D	E
Build Docs				1
	Sub Cover Doc MAP1			2
		Make Doc		3
			Gather Data	4
			Build Doc	4
			Review	4
			Build	4
		Release Doc		3
			Move Doc to "In Review"	5
			Email Manager for review signoff	5
			Create PDF copy and move to "Released MAPs"	5
	Sub Closed Knob Doc MAP2			2
		Make Doc		6
			Gather Data	7
			Build Doc	7
			Review	7
			Build	7
		Release Doc		6
			Move Doc to "In Review"	8
			Email Manager for review signoff	8
			Create PDF copy and move to "Released MAPs"	8

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