Combine trading with the bank and building something in the same action

If you have enough resources to trade with the bank and build something, you should be able to initiate building that thing by placing the object on the board and THEN selecting what resources you give to the bank and what you trade for other resources.
For instance: I have 10 wood, a 2:1 wood port. And I can legally build a city (settlement on the board and not all cities used yet AND the bank has 2 grain and 3 ore) - I click on city and then a trade screen appears. The Gain side displays what I need to get, the give side is empty so I can place enough wood in there to make the trade with the bank work.
Of course, it should be undoable if you do not want to trade with the bank after all... And the building icon should be of different color or with a bank icon to indicate that.
Or: I have 5 wood, brick, wheat. And a settlement to build. Clicking on settlement and where to build it - trade shows I need a sheep so I place 4 woods in the give section. Hitting on bank makes the trade and c