simulink mxArray subscripting not supported

Hello all,

When I try this:

disp(VariableNames(i))

I get an error: Subscripting into an mxArray is not supported.

similar to: http://www.mathworks.com/matlabcentral/answers/13297-subscripting-into-an-mxarray

but with no output other than the command window.

Thanks in advance!