Add the heading "Product 2" to C1 of Worksheet A, and in C2 enter this
formula:

=IF(ISNA(VLOOKUP(A2,'Worksheet B'!A$2:C$300,3,0),0,
VLOOKUP(A2,'Worksheet B'!A$2:C$300,3,0))

(all one formula). Then copy down to C2000 by double clicking the fill
handle with C2 selected (the fill handle is the small black square in
the bottom right corner of the cursor).

Hope this helps.

Pete