If you can only have one record then get rid of the subform. Bind the tables in a query by order ID. Now just add the fields to your main form in tabular fashion. The subform is not doing anything for you if you can not have more than 1 record.
If you can have more than 1 record, but this is a data entry form then set the subform to data entry, make it a single form view, and format the single form view as a tabular form (i.e. stack the labels on top). Remove the navigation buttons on the subform. You could probably do this with a continous form and some code, but I think you would see the new row but be unable to access it.