Ah, I made the REFSMMAT uplink page use the same kind of input format as the real RTCC needed. In most cases I have only done that when a mission planning mode is activated in the RTCC MFD, mostly because that feature still needs a lot of work and manual writing to be usable by all users. But I guess in this case I already require it of every user, at least for now. So what you need to input there is this:
C12 is the code for "Initiate REFSMMAT Update"
CMC is the computer to uplink to, LGC being the other option there.
CUR is the type of REFSMMAT, it's short for current. That is the generally used REFSMMAT type in the MFD, there are others, but only really usable in the mission planning mode.
2 is the code for a desired REFSMMAT uplink. The other option is 1, changing the acutal REFSMMAT in the computer (which you will rarely do).
What I will probably do is simplify this again, so that the only required input is the choice between desired and actual REFSMMAT.