Sorry I don't read that You use VFP 6. There is no hWnd in 6th version. Try this:

#define IDANI_OPEN    1
#define IDANI_CLOSE   2
#define IDANI_CAPTION 3
*!*    Private Type RECT
*!*        Left As Long
*!*        Top As Long
*!*        Right As Long
*!*        Bottom As Long
*!*    End Type
DECLARE LONG FindWindowA IN WIN32API STRING class, STRING title
DECLARE INTEGER SetRect IN WIN32API;
                           STRING @lpRect,;
                           INTEGER X1,;
                           INTEGER Y1,;
                           INTEGER X2,;
                           INTEGER Y2
DECLARE INTEGER DrawAnimatedRects IN WIN32API;
                           INTEGER hWnd,;
                           INTEGER idAni,;
                           STRING  lprcFrom,;
                           STRING  lprcTo
STORE SPACE(16) TO rSource, rDest
STORE 0 TO ScreenWidth, ScreenHeight

** Get _Screen hWnd
lhWnd = FindWindowA(0, _Screen.Caption)

ScreenWidth  = _Screen.Width
ScreenHeight = _Screen.Height

SetRect(@rSource, ScreenWidth, ScreenHeight, ScreenWidth, ScreenHeight)
SetRect(@rDest, 0, 0, 200, 200)
DrawAnimatedRects(lhWnd, BITOR(IDANI_CLOSE,IDANI_CAPTION), rSource, rDest)