Corrected (thanks to Walter Roberson for pointing out the imprecise formulation): Hi, so you are looking for a way to let MATLAB know, when the fluent execution has completed? Generally speaking, when you issue a system command from MATLAB, there are two possible scenarios:
1) MATLAB waits for the system command to complete (and collects its outputs, if any). For example:
[status,cmdout] = system(command)
2) MATLAB issues the command and returns control to the command prompt.
See documentation on running system commands here and here. In your case, you need to make sure to wait for the completion of your first journal, until you start the second.
Also note that your script may again contain commands that either wait for completion or not. It is quite common in Fuent journal files that you just put some tasks into the queue on your HPC server. If you need to wait for completion of the journal file, you must use proper syntax within the journal file itself.