Urgent! how to get area through UDF?

David

The following sentences of UDF are used to get the coordinates and pressure of the centriods on the specified boundary. And also I want to get the area of the face cells on the boundary to calculate the force. Which macro should I employ in this case and how?Thanks.

begin_f_loop(f,t)

{

F_CENTROID(x,f,t);

fprintf(fload3,"%10.5lf %10.5lf %10.5lf %10.5lf\n",x[0],x[1],x[2],F_P(f,t));

}

end_f_loop(f,t)