Hi
VLOOKUP & HLOOKUP formulas can give you misleading results if the target you are searching for is not in your list. For example Vlookup searches from the top of your list downwards, if it can't find your target it may give you the result of the nearest it can get to it - and you will be unaware this is incorrect. Also the list must be in sequential order, alphabetical and numerical or lookup will fail and give you a false result.
However, if you add "false" at the end of the list of arguements these formulas will return an error result if they cannot find an exact match. This is better than false information and allows you to devise strategies to deal with it.
Hope this helps
Regards
Derek