How can I change system cursor in windows?

I want my application change cursor in windows when it’s over some areas in my game. For example - always it’s standart arrow and sometimes it’s hand pointer.
I tried do it with WINAPI using

    [System.Runtime.InteropServices.DllImport("user32.dll", SetLastError = true)]
    static extern int GetWindowLong(System.IntPtr hWnd, int nIndex);
    [System.Runtime.InteropServices.DllImport("user32.dll")]
    static extern System.IntPtr LoadCursor(System.IntPtr hInstance, int lpCursorName);
    [System.Runtime.InteropServices.DllImport("user32.dll")]

and do this

hcursor = LoadCursor(System.IntPtr.Zero, (int)IDC_STANDARD_CURSORS.OCR_HAND);
SetCursor(hcursor);

when I’m changing cursor

But it seems like OS changing it after me. I found this information

If your application must set the
cursor while it is in a window, make
sure the class cursor for the
specified window’s class is set to
NULL. If the class cursor is not NULL,
the system restores the class cursor
each time the mouse is moved.

on MSDN, but i can’t find how to do it. Maybe there is simplier ways control system cursor on windows with unity?

Is there a particular reason why you don’t want to use Cursor.SetCursor (to reset to default just pass: null)? You can easily find a “hand” cursor texture over the web…