Have a look at Aladin's explanation in the following thread...

http://www.mrexcel.com/board2/viewto...ys=0&postorder
=asc&start=0

In article ,
"Nikki" wrote:

I have a genral question regarding the vlookup function. I have noticed that
there are some vlookup fromulas that have a the lookup array that is
1/(condition) for examlpe: =LOOKUP(2,1/(-B11:K11<0),B11:K11), could someone
please explain to me why the array is 1/ divided by the condition? I truly
would appreciate it. Thanks in Advance.

Nikki