We use custom vba programmed lookup functions in excel to match approximate duplicate entries. The custom lookup function allow to search the best match for string value in any database (people names, company names, addresses, etc). If there is 100% match value, it will be found. If there is no 100% match value, the best approximate match will be found. Also there is a function wich returns a percentage estimate of how closely string value 1 matches string value 2. It allows us to compare large data sets just in a few clicks.
For examle if you have 2 databases with people names you can compare this databases even if there are any mistakes in name spelling: [swf:http://xlbin.com/wp-content/uploads/2011/12/fuzzy_lokup.swf 595 446] http://xlbin.com/wp-content/uploads/2011/12/fuzzy_lokup.swf
More complex sample of fuzzy match function we built for our client is a function to match specific string in a text and if there is a match with matching > threshold level to match another substring in the sentence where first sub-string matched. This is how our client can use specific keywords in large amount of manually entered data with multiple typing mistakes.