Apply bus signals to a mux for use in interpreted matlab function block in simulink

I know that bus signals are not to be mixed with a mux in Simulink, but I need to import some variables from a bus used prior in my simulation to a mux. I am using this mux to send my 12 inputs into my interpreted function block. When I run the model I get an error saying "Invalid output port data type." Is there a workaround for this error? Maybe save the bus signals somehow then send them into the mux? Or maybe I do not need to use a mux to send all my signals into the interpreted matlab function block?