Really simple question for a simpleton!

I have started to like custom formatting and often use it for things like

"Year Created = "0000

so that I don't need to have a separate adjacent cell telling the reader
what the value is.

In this case, the cell contents is just a text string with a maximum of 30
characters, mostly all letters and spaces. I don't know what to use (the
equivalent of 0000 for four digits) to tell it to allow any general
character, most likely a letter or space.

Please help.

Thanks
Dean