Concrete brick patio, -how do I temporarily divert the water around a raised deck post?
Why not create a flashing dam around the post areas? 

You could use a roll of sheet aluminum, maybe 6 inches wide. Put a crease down the middle to form an L shape. 

Scrub down the blocks and when dry, duct tape the bottom flange of the aluminum to the blocks. You can bend the corners by cutting the bottom flange to the crease or cut separate pieces and duct tape them together. Add some duct tape to the inside seam along the bottom of the well formed. 

When ready, it should pull up with little to no residue. If necessary, some mineral spirits should remove any remaining adhesive.