Hi vhd,
I understand that you are trying to use a S-Function block in Simulink and modify its parameter values programmatically, instead of changing it in the Mask dialog box. The error you are getting is because you are trying to change the value of the parameter of mask shown as '$_MOUNT_STIFFNESS_X' which is not the actual name of the parameter, but just the prompt text.
To view the actual parameter names of S-function, right-click on the 'FE_014_SIMPACK_demo_01_linear' block and click on Block Parameters. This displays the following:
The parameter that you are trying to modify is 'subvar0'. Similarly if you want to modify '$_MOUNT_STIFFNESS_Y' or '$_MOUNT_STIFFNESS_Z' access subvar1 or subvar2 respectively. Now you can modify the desired parameter as follows:
set_param('FE_014_SIMPACK_demo_01_linear/FE_014_SIMPACK_demo_01_linear','subvar0','60')
