In a previous post I covered the basic setup for validating currency when posting to a GL account if you want to control what currencies are posted. The previous example was just a general journal posting. In a more complex example like a sales flow with invoicing you could use it to validate the invoice before it’s posted. Here is a quick eample
One thing to bare in mind is the operational effect of this. If you print invoices to go with a shipment then not being able to post might hold up a shipment. So you should be ready to have people be able to interpret the messageand correct the documents so that an invoice could be posted and printed.