Think you are more or less limited to defining the fields as text, number, date etc. You can put validation on the field. You can display numbers in different format in a layout with field format. On the validations side (in manage db -> fields -> options) I do not think there is any regex functions, but you could use a string position to check for an occurance or possibly "filterValues" function.
As far as content storage, filemaker pretty much allows anything to be stored, even leading and trailing spaces
you can make the field auto entered calculation and use
Filter ( Customer Name ; "abcdefghijklmnopqrstuvwxyz ABCDEFGHIJKLMNOPQRSTUVWXYZ" )
and uncheck the "Do not replace" option
It seems that he wish to exclude numbers, not capital letters, foreign chars or spaces.
He can try:
Filter ( Customer Name ; KanjiNumeral ( Customer Name ) )
Nice, filter is my new friend to replace some monstrous calculated fields.
Could use Substitute also if there are only a couple of characters you do not want to allow.
I have a solution where the company name field is used to create a folder or define a file path on the server. "/" and "." really mess up the file path. So I used Substitute to replace them with "-" and ""