How to differentiate between bonded and custom cleared inventory when both are from the same locatio

In the past, when i have had to deal with inventory that is located in a bonded warehouse, we have used the country location to drive the fact that it was bonded but in our case now, we have both bonded and non-bonded product stored in the same location. How can we factor this into a tax determining factor so that we know when we are selling from bonded or non-bonded?
I have logged an SR and there is no luck there.

My current thinking it to create 2 sub inventories so that when product comes in it automatically goes to the bonded sub inventory and as goods are custom cleared, they move to the non-bonded sub-inventory. We would create a dummy tax rate called 'BONDED' and when we make sales  from the sub inventory that has the status of bonded, we would insert the tax rate of 'BONDED' intot he tax classification code field and use this to help drive the tax classification. This of course requires a customisation so if anyone has a better way of doign this that i