Not quite what you asked, but I find this technique pretty easy...

Select the range
Format|cells|number tab|custom category
In the "type:" box, put this:
alt-0252;alt-0252;alt-0252;alt-0252

But hit and hold the alt key while you're typing the 0252 from the numeric
keypad.

It should look something like this when you're done.
ü;ü;ü;ü
(umlaut over the lower case u separated by semicolons)

And format that range of cells as Wingdings.

Now, no matter what you type (spacebar, x, anyoldtextatall), you'll see a check
mark.

Hit the delete key on the keyboard to clear the cell.

If you have to use that "checkmark" in later formulas:

=if(a1="","no checkmark","Yes checkmark")

=counta(a1:a10)
would tell you how many "checkmarks" you have in A1:A10.

And you can always filter for that funny character.

Albert wrote:

I'm creating a form with excel and would like to have checkboxes that the
user can click on to have a check appear (or disappear).

--

Dave Peterson