I see two options at the moment, I haven't used SABNZBD before however...
1st, it seems that SABNZBD has the ability to run scripts after jobs are completed, it may be possible to add a script that calls the MC command line utility..http://wiki.sabnzbd.org/user-scripts
2nd you may have to create a batch file such that SABNZBD is called first & then MC Command is called second.
Call SABNZBD.exe (required parameters)
Call mc_com.exe (required parameters)
this way the batch files containing these instructions is paused until each of the programs actually called have finished.