Hides the cursor on a window. Even the titlebar

HideCursor.c

// Hide cursor 

LRESULT CALLBACK dialogProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
    switch(msg)
    {
        // put this in your dialogProc
        case WM_SETCURSOR:
            SetCursor(NULL);
            return TRUE;
    }
}