function GetValue(dbf, f :integer): double;

GetValue reads the specified field from internal memory.
Be careful. The first field has a number 0 and the last field has a number FieldCount-1.
You have to read a record with ReadRecord before using GetValue.
It returns a double value for numeric fields (Numeric, Float, Double, Currency, Integer).

var
  dbf :integer;
  r :integer;
begin
  dbf := OpenBase( 'filename.dbf' );
  if dbf <> 0 then
  begin
    for r := 0 to RecCount(dbf)-1 do
    begin
      ReadRecord(dbf, r);
      showmessage( GetValue(dbf, 1) );
    end;
    CloseBase(dbf);
  end;
end.