"Quantity Needed" text box for market orders

Hey, guys. Just a little suggestion that would make buying from the market much faster.

Say you want to build something and you need 3,000 iron. You have 1,643 iron in stock. So you go to the market to buy iron and you sit there a moment to make a calculation in your head... 3,000 minus 1,643 equals 1,357. OK. So you enter 1,357 in the text box and you buy that amount.

If you have to run these calculations for one purchase, that's ok. But if you are building a building and a unit, and have to do these calculations for multiple commodities one after the other, it gets pretty annoying. You don't want to overbuy materials or you might not have enough cash to buy everything you need.

Why not add a text box labelled: "Quantity Needed". In the above example, after clicking on another player's iron offer, all we would need to do is enter "3000" in the Quantity Needed box. The program would then look at the amount of iron we have in stock, subtract it from the Quantity Needed, and automatically buy only the amount we are looking for, in this case 1,357... without us having to run the calculation ourselves.