How to change MATLAB workspace variable with set_param command

In the help section of set_param command, it is written that "After you set parameters in the MATLAB® workspace, to see the changes in a model, update the diagram. set_param(model,'SimulationCommand','Update')" But, I am not able to change the workspace parameters with set_param command in an embedded function in Simulink. I tried 'base workspace' as the object of set_param but it gave error "'base workspace' is not a valid model name because it is not a valid MATLAB function name." Any advices?