How can I enable signal logging in simulink for select times during a simulation?

I'm using Matlab Version 7.10.499; Simulink version 7.5.

I have a large bus designed to compile data generated during a simulation, and I have enabled signal logging on the bus. The simulation can run for a long time, and I sometimes run out of memory, so I would like to enable signal logging partway though the simulation.

So far I've tried the solution here: http://www.mathworks.com/help/simulink/ug/configuring-a-signal-for-signal-logging.html#bsw9nl4-3

I have tried to turn off signal logging, start then simulation, then I pause the simulation and use "set_param(ph.Outport(1),'DataLogging','on')".

When I do this, the little antenna symbol that indicates that signal logging is on shows up, but the simulation fails to generate the logsout object that is supposed to contain signal data.

I tried the same thing with a different command mentioned here: http://www.mathworks.com/help/simulink/ug/enabling-signal-logging-for-a-model.html

In this case the command is "set_param(bdroot, 'SignalLoggingSaveFormat', 'Dataset')"

Similar results. I can't get logsout to contain partial data. It either has all of the data or it isn't generated at all.

Any help is appreciated.