I take it that the files are actually named A.bmx, B.bmx and C.bmx. If so then the correct thing to do would be to put the following into your main file A.bmx:
That's how I do it. There doesn't appear to be a problem with the order of definitions in the respective files.
Import "B.bmx" Import "C.bmx"
That's how I do it. There doesn't appear to be a problem with the order of definitions in the respective files.