Lets say you want to have Figure 1 put their hand on Figure 2's hip as if they are dancing. Constrain the prop to Figure 2's hip and adjust the position to were you want it. You should then be able to move figure 2 around and the box follows the figures hip. Then Constrain Figure 1's hand to the box. Figure 2 moves box moves and Figure 1's hand moves.

Poser 5, 6, 7, 8, Poser Pro 9 (2012), 10 (2014), 11, 12, 13