for I := 0 to DBGrid1.Columns.Count -1 do
if DBGrid1.Columns[I].FieldName = 'LOT_NUM' then
begin
DBGrid1.DataSource.DataSet.First;
while not DBGrid1.DataSource.DataSet.EOF do
begin
showmessage(DBGrid1.Fields[I].AsString);
DBGrid1.DataSource.DataSet.Next;
end;
end;