can... just set your D7D as Flash : WL mode.
then set your 5600HS as WL also, press mode, den WL : on (i think... no camera or flash with me now) then set the flash to manual, 1/32 1/16, 1/8, etc...
if i am not wrong, can set 2:1 with the 2 flash also... anyway, i dun have 2 flash to try...
remember to face the IR receiver facing the camera body. or visible to the camera body's flash