The OPEN-CLOSETBL is an unusual approach. I have always used report design (spacing, line control, textbox position, text alignment, color/shading) to indicate beginning and ending of records and sections. Instead of this table to provide text for textboxes, could have just built labels in report.
I presume IDCustomer is customer identifier. Looks like each customer can have multiple orders.
When you create a group section, should put fields/controls in that section. So if you have a customer header then put customer info into that section. If you have an order # header then put order info into that section. Then info on associated parts will be in detail section. So put the OPEN-CLOSETBL fields into appropriate group header/footer section as well. Have to activate footer section for each group. Order groups in whatever hierarchy you want, probably customer then order. Then could apply a sort on part identifier if you want.
Should probably use & instead of + for concatenation. The + returns Null when field is null so the prefix text will not show and end up with a lot of confusing white space. Why not using labels instead of concatenating?
Advise not to use all caps in naming convention - it is harder to read. Better would be OrdersTBL, OrdersQRY, OrdersSubrpt. Also should avoid spaces and punctuation/special characters (underscore only exception).
This is not a normalized data structure.