How do I provide input to a Simulink model without placing it in the workspace

I have a Simulink model that is currently being run from a script (i.e. not a function). The script writes variable values to the MATLAB workspace, runs the model simulation (which uses these values), and then the model writes additional values to the workspace. If I try to convert the script into a function (i.e. by placing function [output] = runSim() at the top of the file) then Simulink complains that it doesn't know about the variables, presumably because they are not in the MATLAB workspace, but rather they are in the function scope.

Is there an elegant way to provide a Simulink model with inputs and take outputs from a Simulink model other than sticking them into the workspace?