Thanks so much for the responses Gang and Rick. It doesn't have to be with DM, I hope I didn't give that impression. I just wish to have SPMG or GAM functions varying in duration across trials (e.g. if I have onscreen stimuli lasting from 4-12 seconds, randomized). So there's no way to do this with AFNI? Or am I missing something? What I'm looking for is akin to FSL Feat's 3-column-format convolution (where column 1 is onset, 2 is duration, and 3 is total value) with an FSL Feat double-gamma HRF. Thanks in advance for any help!