Goal Seek Type Formula

[jjramirez85]

I have a total cell ($.024046) that sums all rows above which contain 1 blank cell (XXXX). On the side is a cell which equals 80% of the total cell ($0.19). How can I make the blank cell match the cell returning 80% of the total. With trial and error, $.32 in the blank cell will output $.32 as 80% of the total. They match. How can I match with formula? I tried goal seek but it did not work.

Reference: Ext cost = qty x unit cost

Component	UOM	QTY	UNIT COST	EXT COST
123451	LBS.	0.5100	$ 0.2454	$0.12515
123452	LBS.	0.0007	$ 8.3360	$0.00591
123453	LBS.	0.0019	$ 0.5523	$0.00105
123454	LBS.	0.0397	$ 0.0818	$0.00324
123455	LBS.	0.0033	$ 0.1850	$0.00062
123456	LBS.	0.0041	$ 1.0573	$0.00429
123457	LBS.	0.0054	$ 1.6464	$0.00896
123458	LBS.	0.0434	$ 0.7721	$0.03355
123459	LBS.	0.0003	$ 2.6779	$0.00083		Return	80%
123460	LBS.	0.5000	XXXX	$0.00000		$0.19
123461	LBS.	0.0005	$ 6.7730	$0.00354
123462	LBS.	0.0192	$ 0.7523	$0.01441
123463	LBS.	0.0007	$ 1.2633	$0.00085
123464	LBS.	0.0048	$ 7.9713	$0.03805
				$0.24046

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[jjramirez85]

https://drive.google.com/file/d/1RzJxVeF87W-15VgrKeUEtSYvcU_J_8vl/view?usp=sharing

When summing ext cost to equal total cost, and returns being 80% of total cost, the $0.19 must equal the same value returned as $0.3206.

The goal seek in the previous example by the other member solves the problem, but I want in formula.

I have your data in A1:E16 with the total in E16.
Formula in G16: =0.8*(E16)/(1-0.8*(C11))
I don't get a circular ref.

Component	UOM	QTY	UNIT COST	EXT COST
123451	LBS.	0.51000	0.24540	0.12515
123452	LBS.	0.00070	8.33600	0.00591
123453	LBS.	0.00190	0.55230	0.00105
123454	LBS.	0.03970	0.08180	0.00324
123455	LBS.	0.00330	0.18500	0.00062
123456	LBS.	0.00410	1.05730	0.00429
123457	LBS.	0.00540	1.64640	0.00896
123458	LBS.	0.04340	0.77210	0.03355
123459	LBS.	0.00030	2.67790	0.00083		Return	80%
123460	LBS.	0.50000	XXXX	0.00000		$0.19
123461	LBS.	0.00050	6.77300	0.00354
123462	LBS.	0.01920	0.75230	0.01441
123463	LBS.	0.00070	1.26330	0.00085
123464	LBS.	0.00480	7.97130	0.03805
				0.24045		0.3206

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