Polyface Mesh to 3d Solid - lsp???

[luckysairs]

Hi everyone,
I am very new to cad. I am a Design student and I have a design that I have modeled in Sketchup. I've imported it into AutoCad and my end desire is to import the autocad file into 3ds max and render it for my presentation. The file I have imported into 3ds max currently won't let me render it properly and I suspect this is because it is a Polyface Mesh and not a 3D Solid. I know this topic has been covered in other threads but the solutions which were suggested were "CONVTOSOLID" command and routine files ".lsp"
I have tried CONVTOSOLID and it doesn't work and I have absolutely no idea what to do with a ".lsp"
Please help !

[ReMark]

Instructions on using a LISP routine can be found in the CADTutor AutoCAD FAQ section. Look under Customisation for How do I use an AutoLISP routine?

If CONVTOSOLID did not work what LISP routine were you looking to use?