how to pass argument from c/c++ to function handle in matlab: Mexcallmatlab

I noticed this post. http://www.mathworks.com/matlabcentral/answers/96775-how-do-i-pass-function-handles-to-c-mex-function-in-matlab-7-8-r2009a

where a simple example is given:

h = @cos;
x =0.6;
y = simplefunction(h,x);

the function is evaluated through "mexCallMATLAB(1,&lhs,2,rhs,"feval")"

now I need to pass some argument to this function handle, for example:

h= @(x,a) a*cos(x), where a is supposed to be parsed from simplefunction.c

how can I do that?