Formula (array?) to list unique entries that match criteria?

In D2 enter this array formula and copy down

=IFERROR(INDEX($C$2:$C$11,MATCH(0,IF(B$2:B$11>0,"",COUNTIF(D$1:$D1, $C$2:$C$11)),)),"")

...confirmed by pressing CTRL+SHIFT+ENTER to activate the array, not just ENTER. You will know the array is active when you see curly braces { } appear around your formula. If you do not CTRL+SHIFT+ENTER you will get an error or a clearly incorrect answer. Press F2 on that cell and try again.

Row\Col	A	B	C	D
1	ITEM	QTY	LOCATION
2	Item 1	-1	Location 1	Location 1
3	Item 2	1	Location 2	Location 3
4	Item 3	-1	Location 3	Location 2
5	Item 4	1	Location 3
6	Item 5	-1	Location 3
7	Item 6	1	Location 3
8	Item 7	-1	Location 3
9	Item 8	1	Location 4
10	Item 9	-1	Location 2
11	Item 10	1	Location 3

Row\Col	A	B	C	D	E	F
1	ITEM	QTY	LOCATION	LOC_RESULTS	LOC_TO_MATCH	ITEMS_MATCH
2	Item 1	-1	Location 1	Location 1	Location 3	Item 3
3	Item 2	1	Location 2	Location 3		Item 5
4	Item 3	-1	Location 3	Location 2		Item 7
5	Item 4	1	Location 3
6	Item 5	-1	Location 3
7	Item 6	1	Location 3
8	Item 7	-1	Location 3
9	Item 8	1	Location 4
10	Item 9	-1	Location 2
11	Item 10	1	Location 3

Okay,
I'm using this as a form generator, and the table above is close to how I will be using the data. I NEED the array formula in column F to list unique items from column "A" that meet two criteria:
1) if the value in column "C" matches cell $E$2
2) if the value in column "B" is a negative value.

This is the final hurdle, then the rest of this form generator is smooth sailing.

Thanks for all of you help so far, I really appreciate it!