Change standard action if inventory is open?

My main interface has 5 commands:

* walk (standard action while playing)
* look (can select via coin interface)
* talk/eat (can select via coin interface)
* pick up/use (can select via coin interface)
* use with (combined command with drag mode, should be the standard action if inventory is open)

At the moment, if my inventory is open, the standard action is "walk to inventory object". What is the best way to set the "use with" action as standard, as long as the inventory is open? Other question: It is possible to take the item "in hand" that the item graphic jumps from the inventory slot to the mouse cursor?