um... oh, ick. normally, i'd fix this in ray dream, but don't know if coreldream has the same tools. since you exported as dxf instead of obj, i'm going to guess it doesn't. try selecting the upper and lower table top as you have been, then deselecting the lower plane polygons. (use the same key, it's ctrl.... if i recall.) normally the grouping tool selects both sides if you are in wireframe mode, and only the front side if you are in some type of shaded mode. you might try going into shaded mode and selecting the polys from the underside; it might only see the top inverted ones. or, you might try using a marquee select in a side view to grab the top plane polys.