then create a trigger which detects when a unit is ordered targeting an item, check if the order is to pick it up and check if the target item is a tome, if yes, put it into the inventory and make the hero use it...
or you can just make a trigger which runs when the unit picks up an item, check if it was a tome and order him to use it... now on the trigger where you give the unit a tome, disable the use trigger first before giving tome, then enable it afterwards
or you can create two versions of tome, one with the use auto turned on, one with it turned off... you give the hero the turned off version, then create a trigger such that when he drops it, you change it into the turned on version...
@SonofJay - if you read his post, he already knows that... but he wants it such that if he drops it and picks it up, it will be like the use automatically is on again