Dialog parameter not updating in C Mex S-Function

Hi, I am trying to simulate my c code using S-function where calibrations are passed through dialog parameter. my parameter in workspace is a structure of parameter variables. When I simulate my s-function, parameter is correctly passed into s-function. But when I change value of one of parameter in my parameter structure, updated value does not reflect in s-function simulation after change.

To update parameter value in s-function in next simulation step, I had to clear workspace, load parameters again, change the value of desired parameter and simulate. I had to do this every time I want to change parameter value. Any explanation why this happening and how to solve this.

Thanks Mukesh