MarbleBlastMap2Dif (aka MBMap2Dif) is a program that allows converting MAP files made in interior-building programs like the Torque Constructor or QuArK to DIF files, so that they can be used in Marble Blast levels.
Take your MAP file and drag it into MBMap2Dif, making sure all the textures you used into it are in the same directory as MBMap2Dif, so that it works properly. It does not work with CLX or CSX ones.
Some drawbacks are not excluded, and these drawbacks are converting errors. There's a large number or errors level builders can encounter, and they must go back editing to fix the eventual errors quoted in the error message box, which sometimes discourage them as deeply as they must abort their projects.