as long as they hasnt removed his hand they may move it to another square, though must still move the piece. If they cease contact with the piece it is the end of their move.
Touch Move Rule

If a player drop a piece on a square, but his hand is still holding the piece, can he move it on another square, is it legal? Does anybody know a link on this rule.
http://www.fide.com/component/handbook/?id=124&view=article
Article 4.
If a player drop a piece on a square, but his hand is still holding the piece, can he move it on another square, is it legal? Does anybody know a link on this rule.