Simout output from sim command called from Matlab Function Block in Simulink

I'm trying to simulate a model "inner.mdl" (several timesteps) in one timestep of the root model "outer.mdl". I thought of calling simout = sim("inner.mdl") from a Matlab Function Block. The problem is: Since I'm using extrinsic sim (bypassing code generation), simout is returned as an MxArray and I am unable to retrieve the logged signals from it. Any ideas would be appreciated, whether they are about doing this simulation-in-simulation or with obtaining the logged signals using the method I'm trying.