Sure,  I would create a customer invoice when they leave your main location that would take them out of inventory.  You could also move them to the new offsite inventory in the same transaction.  I would use the original cost so it would not change the income statement.   

When they come back in you would need to re-enter them as a new purchase to put them back to the original inventory, remove them from offsite inventory and pay your vendor.  The new inventory cost must be a total of all costs rolled into one number. 

If you need help setting up this process, we would be happy to consult with you but there would be a fee for our service. 

Regards, 

Shirley Byard, owner Best Business Strategies [email protected]