afni.nimh.nih.gov

So I understand the dummy coding now and it should be the following for my three groups:
grp2 grp3
grp1 0 0
grp2 1 0
grp3 0 1

For the 3MEMA format, do you list all the files under the same set? How would it know who is in which group?
Also how is this method different from doing 3 separate 3dMEMAs , one for grp1 vs grp2, one for grp1 vs grp3, and one for grp2 vs grp 3?

Thanks!