clone object on poly

hello
I would like to clone(instance) an picked object on selected poly of an selected object. Grrrrr... lot of time, for nothing... if somebody can help... Thanks

OBJS = $
rollout pick_box_test "Object to clone"
(
pickbutton chooseit "Pick" width:140
on chooseit picked PO do
(
ALLFOBJS= polyop.getFaceselection OBJS as array
for NF = 1 to ALLFOBJS.count do
(
BBB = instance PO
>>>>> BBB.pos of the center of the poly
>>>>> BB.rotation of the selected poly
)
)
)
createDialog pick_box_test