I have only looked at this very briefly, so far. It should be possible to download NASM from sourceforge, go to Project options -> Macros tab, and edit the AS macro (to something like C:\NASM\blah blah) - removing the default "ML.EXE".
I can import the project file into the IDE, and when I try building, ML complains about the first ASM file (the syntax). Maybe it works if NASM is installed (I havn't tried it)??
Pelle