I need help with this one. I have one excel file with three worksheets. I
want to compare the data in column A in each worksheet and if a value exists
in more than one sheet I'd like to highlight the cell in each sheet it
exists. Or I guess another way to put it is I want to higlight all values in
the A columns that are not unique across all three worksheets.

For example:
Sheet1
Column A
apple
orange (would be highlighted)
banana

Sheet2
Column B
orange (would be highlighted)
melon (would be highlighted)

Sheet 2
Column A
peach
melon (would be highlighted)

Thank you!
Sarah