MFC is C++, right?
If so, you can just use clock()
.
#include <ctime>
clock_t time1 = clock();
// do something heavy
clock_t time2 = clock();
clock_t timediff = time2 - time1;
float timediff_sec = ((float)timediff) / CLOCKS_PER_SEC;
This will usually give you millisecond precision.