How do I make a specific checkbox usable/clickable (not read-only) whilst a form is opened with acFormReadOnly in Microsoft Access?

We've got a checkbox on a form that we'd like to be able to check/uncheck even whilst the form is opened as read-only (it's a sales/product form and when an order has been invoiced, we want to prevent changes).

I know I could add a command button in its place and even make that button look like it's a checkbox with some images, or even set up a key combination to be used instead of the checkbox, but first I'd like to know if it's possible to simply exclude one checkbox from being read-only on a read-only form.