Thanks for the indications!
I had a look at the model_*.c file, and even if I've never worked with C before, I think I understood a bit how this works, especially when looking at the simpler model_sinewave_ap.c. But I got totally stuck at understanding how time and event times are defined and convolved in model_conv_diffgamma.c, which is the model I need.
I should also mention that I actually have two event types to model within the same time series. As far as I understand, I think this is also something that would need to be programmed in the model_*.c, right?
Bottom line, although I'd love to learn a new language, it seems a too big challenge for the timeline I'm constrained to. Unless a very generous soul is willing to create a model_*.c that can handle sub-TR events of more than one types, I'll have no choice but to turn back to the evil Matlab who's holding me captive in its matix world.
Sincerely!