how to compare string in a column then copy data if string doesn't match

how to compare string in a column then copy data if string doesn't match

References

Reference NO 1

http://stackoverflow.com/questions/15194591/how-to-compare-string-in-a-column-then-copy-data-if-string-doesnt-match

Reference NO 2

http://www.teachexcel.com/excel-help/excel-how-to.php?i=55537

Reference NO 3

http://office.microsoft.com/en-us/excel-help/guidelines-and-examples-of-array-formulas-HA010228458.aspx

Reference NO 4

http://www.eng.auburn.edu/~tplacek/courses/3600/Strings%20and%20Manipulations.htm

Reference NO 5

http://en.kioskea.net/forum/affich-100231-comparing-columns-and-returning-value

Reference NO 6

http://www.techonthenet.com/excel/macros/copy_data4.php

Reference NO 7

http://www.techonthenet.com/excel/macros/copy_data4.php

Reference NO 8

http://excel.bigresource.com/Lookup-up-Match-return-a-value-in-column-A-if-my-data-matches-column-B--2NXLhbnN.html