Hi,
I suppose adding an apostrophe to the beginning of your formula cells would do what you're after but I think all you really need to do is convert the formulas to values.
Try highlighting (selecting) your entire range of formulas and press Ctrl + C. Then simply press F10 and then V.
This will copy those formulas and paste special them as values.
If you're really set on adding the apostrophes, I can think of a way to do it with vba, but I think copying & pasting as values might be better.
Hope it helps.