Make few of Invoice header fields read only after Invoice validation

Summary:

We need to customize Payables Invoice Screen.
Based on Invoice Validation and approval Status, we need to make some fields such as Supplier, Invoice Number etc non editable when status is Validated.

We are trying to achieve same using Sandboxes and Page composer.
But while adding EL expression on fields at Invoice Header level, we are not getting Validation Status or approval status in binding params list.

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