I have a character who is in the middle of a fight and doesn't have a knife in his hand but after dodging a punch or two decides to pull a knife out of his back pocket. I've successfully been able to attach the knife to the hand and have it placed perfectly and have keyframed in iclone that the knife visibility is OFF UNTIL the character puts his hand behind his back where the visibility is then key framed on and the knife successfully appears. This worked in iclone however when I export over to Unreal Engine he always has the knife in his hand at every given point.