Invoicing and receiving process

Hi guys! I need some ideas . These are my processesses. How can i represent them in navision 4. I order 120 units at 1.20$ from my supplier. Because of customs and another third party system used for customs, I receive the next day the invoice and the packing slip where qty and costs are not the same: 100 units instead of 120; 1.22$ instead of 1.20$. I need to enter those information( 100 units and 1.20$) in Navision where an Interface must be built to be connected to the customs software. In the meantime, I physically receive goods anf after opening boxes, I found that i have only 95 units ( it can be more than 120 or even less). I then need to enter real qty received and qty invoiced in both Navision and the custom software. So my question is: How can I manage that scenario in Navision keeping in mind that the initial invoice from the supplier is important and must be enter in both system even if it is wrong. Thanks for any help.

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