... the round after the target stops moving?
Target hunkers down, thinking he's safe behind cover.
Target stays put his next turn, only popping up to lay down suppressive fire. Ranged attacks against him are at +1D6.
Lather, rinse, repeat for the next round, with ranged attacks now getting a +2D6 bonus.
Target smartens up, and moves his next turn. Ranged attacks against him lose the bonus, resetting the 'clock' should Target Boy stay hunkered down in his new spot on the battlefield.