surface on grid trouble

Hi guys,

I was wandering if anyone can help me with a definition that gives me trouble.. I have this grid which I deform using lines or points. In the end I get boxes in different heights and dimensions. What I need now is to flow a surface along the top of the boxes but I'm having trouble of making it, so every time I'm baking the result and working it out in rhino. The thing is that I think it should be possible to make it in grasshopper, as I want to be able to see the surface and make changes if I have to, before it's baked. I have attached the files I've been working on. Any ideas?