[NVC-V.I.P]

I have created a 5 column table in Word 2007 and need to get the 4th column
to display the percentage difference between columns 2 and 3 automatically.
e.g. if column 2 is 300 and colomn 3 is 30 I'd like column 4 to display 10%
etc. I am at a loss as how to do this and would appreciate any input!! Thanks!