Is it possible to create something similar to what is called input masks in
Access?

For example, in my Excel spreadsheet I want to be able to type a 9-digit
account number (which contains letters and numbers) into a cell and
automatically have a hyphen inserted after the first four characters. Also, I
want to be able to designate a default value (2007) that will appear in all
the cells of a column, but which the user can change to a different value
when neccessary (for example, 2006, or 2006-2007).

I think that I should be able to do this with a custom cell format, but I
have not been able to achieve this. Does anyone have any guidance to offer?
It would be MUCH appreciated!!