Nice - I got it running with RichMasm. All it needs is the attached batch file extracted as \Masm64\MbMasm64.bat, plus one comment in the actual source:
include \masm64\include64\masm64rt.inc ; OPT_Batch \Masm64\MbMasm64.bat
You may have to hit F6 twice in RichMasm. I've tested it with some of the \Masm64\Examples\* sources, so far without problems. For example, \Masm64\Examples\Advanced\JpgTool\JpgTool.asm (one of the bigger sources) works like a charm :thumbsup:
Grab the latest RichMasm here (http://masm32.com/board/index.php?topic=94.0), extract the attached files to some folder, then move only the file MbMasm64.bat over to its location \Masm64\MbMasm64.bat, open the Edit64.asc and hit F6 (twice, the first time it throws an error - will have to investigate why). As usual, no saving needed. Test it by clicking into the bookmark the dialog to the right, then change e.g. Floating points into Floating points, too and hit F6 :biggrin: