Data Validation for limiting user entry

Is there a custom data validation that will not allow a user to enter no more than One Capital Letter or one Upper Case String that represents a person First Name and not allow them to follow it with a space and the Middle Initial?
For example: Tom or J but not Tom D. or JC

Great I think your suggested would work well. The cell is Upper case only, first Name, but nothing else, one of my 9 users insists on adding a middle initial but it is totally unnecessary and useless as the middle initial doesn't really serve any purpose. To answer your question TOM is not valid since it is ALL UPPER CASE and I want it to only accept Title or Proper Case.

Hi

You can add the "proper" check to the data validation.

=AND(ISERROR(FIND(" ",A1)),EXACT(A1,PROPER(A1))=TRUE)=TRUE

Try and let us know.