Set a Counter Field

Order Table   Item Table    Counter Table
    Order ID     Order ID      Count

Answer:
I don't know if you'd necessarily call it easy, but to set a counter field, I've found it best to use the AfterInsert method on the Master table of the relationship, so the counter gets carried down to any detail tables. For instance, let's say you have a Counter table called Counter with a field called CountVal, that stores your current counter. I'd do something like this:

function TMainForm.GetNewCountVal : Integer;
begin
  with Counter do begin
    Edit;
    FieldByName('CountVal').AsInteger := 
    FieldByName('CountVal').AsInteger + 1;
    Post;
    Result := FieldByName('CountVal').AsInteger;
  end;
end;

procedure TMainForm.Table1AfterInsert(DataSet: TDataSet);
begin
  with Table1 do begin
    if (State <> dsEdit) then
      Edit;
    FieldByName('Order Id').AsInteger :=
       GetNewCountVal;
  end;
end;