Available in FORMS 5-2 SP2 and later.
Form object
Returns a bit string that indicates whether or not the field is filled in.
For a single field, the result is 1 or 0. For an indexed field, the string contains one character per index.
"Frequency" is an indexed mark field with four indexes:
On a form object where the first, third, and fourth "Frequency" fields are filled in, calling Form.GetBitRepresentationString("Frequency") returns "1011".