Inventory Control

I wasn't certain where to post this and perhaps someone already has a solution. Let's say I build a deck and in that deck I have a By Force from Amonkhet and that one copy is in my Inventory as well. Then I go and paste in another deck that I'd like to work towards building that also has By Force in it. The system currently shows that one copy of By Force as being in both decks despite only having one in inventory.
For the life of me, I cannot figure out how to lock a specific card from my inventory into a deck and NOT being "available" for another deck. Anyone have a solution?