A motorized window blind includes a slotted motorized track member mounted to a vertical wall structure of a building and extending across the top of an opening in the wall. It also includes at least two panels mounted to the track and covering the wall opening while being in a position where the panels are parallel and coplanar with one another. The motorized track member has at least one motorized actuation system enabling one panel to move forward away from the opening thereby freeing the track for the second panel to laterally slide behind the first panel. The panels become stacked in a parallel superimposed position in relation with one another. In the stacked position, the panels cover a portion of one end of the opening while completely uncovering a potion at the other end of the opening.