This is what I use to swap items in inventory spaces. 
	public boolean swapItems(int slot1, int slot2) throws InterruptedException {
		if (getInventory().isItemSelected()) {
			getInventory().deselectItem();
		}
		return getMouse().continualClick(getInventory().getMouseDestination(slot1), new Condition() {
			@Override
			public boolean evaluate() {
				getMouse().move(getInventory().getMouseDestination(slot2), true);
				return getInventory().getMouseDestination(slot2).getBoundingBox().contains(getMouse().getPosition());
			}
		});
	}
Kinda messy, but it works.