an idea!

make a two combo copies of the tile you want to use for the entrances...(like the shop door tile, for example)...have one tile an overhead combo and the other be a cave, cave 2, stairs, whatever..have the first be an entrance thats on the very top of the screen...make your side warp...then make the tile warp and wahla!...its an ok idea i admit, cuz you must make the one warp on the top of the screen and the rest of the top has to be unwalkable...but in certain situations, it could get the job done...