use of readfile for usb hid read operation on windows

I am using ReadFile api to read hid device on windows.This function gives same data every time from input buffer after first successful operation and keep on firing same event.When i clear input buffer then it goes in blocking mode and does not respond to further input from device. So my question is how to use ReadFile to read hid device in synchronous mode or asynchronous mode to continue read data from device. I am facing this issue only when i am unable to clear buffer. But after cleared buffer device become unresponsive.