Use of set_param inside an embedded Matlab function: delay observed

Hello,

I want to modify the value of a gain during simulation using the simple enclosed simulink model and including the following Matlab function (previously EML).

function ChangeParam(time) 
coder.extrinsic('set_param');
coder.extrinsic('num2str');
  if time == 10,
   set_param('untitled1/Constant','Value',num2str(1)); 
end

Modification occurs but at time t=11 sec (sample time = 1sec) whereas I would like the modification to occur at time = 10 sec.

Is there a way to ensure that modification occurs at the current cycle? Is there a way to ensure that the Matlab function runs before the computation that uses the constant block?

Regards,