Highlight duplicate entries from multiple sheets

Hy all!

I am trying to highlight duplicate entries from different worksheets using conditional formating and is not woking. I've found this formula =NOT(ISERROR(VLOOKUP(A1;bannedworkers;1;0))) but it not works ; i'm using excell 2003.
I have two worksheets;in the first sheet on the first column (A) named bannedworkers I have a list of banned workers and in the second sheet on the first column (A) I have a list with workers. I want that when I type a banned workers name in the second sheet, first column, the cell to highlight in the color chosen in the conditional formatting.
I've used this formula in conditional formating but it not works =NOT(ISERROR(VLOOKUP(A1;myColumn;1;0))).

What is the problem???

The formula is from here (they say it works) http://www.computing.net/answers/off...ries/5159.html

I've attached a sample of what I want to do!!!