If field contains an alpha character

I have a field that contains text values and I want to be able to filter a report to show only the records where the field does not contain alpha characters (i.e. only numbers and symbols).  My thought process at the moment is to create a calculated column to filter the report like this:

IF( 
  Contains([Field], "A") OR
  Contains([Field], "B") OR
  ...
  Contains([Field], "Z"),
"True", "False")

Obviously, this formula is not very elegant.  Does anyone know of a more efficient way to code this?

Thanks in advance.