You can manually set the currently held item with the set item action part but you would need to create cursors for each item if you want it to also change the cursor to the currently selected item.
Seeing as you said you are using a single command interface I assume that means you are controlling the mouse cursors that will be displayed when mouse cursor enters & leaves scene objects etc? If this is the case then you should probably consider creating a condition "item_held" that will should be set to true whenever you select an item & should be reset to false after you use/remove the currently held item.
So in your object mouse over/out actions you would need to wrap the set cursor action inside of an if query...
if condition "item_held" is false
... to prevent it changing cursor on mouse enter leave unless an item is currently not being held.
Um you do know that there is a dragged item system no? Inside of the game tab is an option to "allow dragging of items from inventory". The "items can be dragged with this command" option inside of the buttons command properties tab. What this will do is automatically change the cursor to the item image/animation & will change back to default once dropped or after you right click to clear.
As for the right click action: That would be created in the mouse properties
tab under game