Help match data using LOOKUP

[Sean15]

Hi,
I saw this post here Any clever solutions to speed up a 50,000 row MATCH formula? and I find it useful. I didn't want to piggyback so I've opened a new thread. I'm getting some odd results using my data. The concept is still the same. I'm trying to find data in column B not in column A. I've sorted column A in ascending order. Why is formula in C7 and C8 returning #NA and not N?

Book1
	A	B	C
1	Blacksmith W	Jane W	N
2	Jane T	paul S	N
3	Judith H	Sam W	N
4	paul V	Judith H
5	Pepper S	Salt Y
6	Salt Y	Pepper	N
7	Sam X	Blacksmith	#N/A
8		Beth	#N/A
9		Rock	N
10		Dsoldier	N
11		cat	N
12		paul V
13		pepper S
14			#N/A
15			#N/A
16			#N/A
Sheet1

Cell Formulas
Range	Formula
C1:C16	C1	=IF(LOOKUP(B1,A:A)=B1,"","N")

 

[Fluff]

If you drop column A down one cell & put an "a" in A1, you should be ok, as long as none of the values in col b start with a number.