My excel program is only typing one letter/number in a box at a time.
Each time I type a new letter/number it replaces the old letter. I
can't figure out what I accidently hit to cause this problem. It is not
in the "vertical" mode. I have restarted excel and my computer, but
nothing helps.

Any ideas would be appreciated as I am in the middle of a complicated
spread sheet.

Thanks,
Marilyn