What do you mean by "calculate" in this context?
A script could be set up that finds all records with a specified value in this check box field. That script can be performed via script trigger each time you access the layout for viewing those invoices.
A relationship could be set up and then a portal--which might or might not be a filtered portal could also list these same invoices as rows of data in a portal. That would not require scripting to set up.
For some examples of scripted finds, see this thread: Scripted Find Examples