Need to make invoice line level global DFF read only when the invoice is validated and accounted

Summary:

Hi,

We have a requirement to make the invoice line level global DFF's readonly once the invoice is validated and accounted.

If the invoice is not validated or if the invoice is validated but not accounted then these line level DFF's should be editable.

We were able to make these DFF's readonly based on the validation status using below expression in page composer.

#{bindings.ApprovalStatus.inputValue == 'APPROVED' ? true : false}

But we are unable to check the accounting status from these DFF's via page composer.

Could someone please let me know how can we check the accounting status from Invoice line DFF using page composer?