Need help accessing line-level attributes from header section (Page Composer / personalization)

Hi everyone,

I’m working on a Sales Order page personalization in Oracle Fusion (25C).
The requirement is to make a header-level field read-only whenever any order line has a Line Category Code = RETURN (or Return Goods).

After some analysis, here’s what I’ve found so far:

• Page Composer EL doesn’t seem to allow referencing line-level attributes or iterating through lines.
• There are few line level fields available eg: bindings.CategoryCode.inputValue; but they are not consistent as it returns value of only the 1st line and no valid way to iterate through lines.
• There’s no header attribute that directly identifies an order as an RMA.