k so this is what i've got :
set a boolean variable to the object
Mouse on left button click object set variable as true
pick instance with UID
object.UID
Mouse Cursor is over object
Mouse Left Button is down set position(mouse.x,mouse.y)
pick instance with UID set variable false
object.UID
it works quite well BUT, as soon as i click one of the objects, the instances of the object all disappear...weird?