Dear Sir,

I want to use following with my own form
I have written all codes with form but could not understand how to use last function
FUNCTION buf2dword(lcBuffer)
Where to use this in form and how?

LOCAL oForm 
oForm = CreateObject("Tform") 
oForm.Show(1) 
* end of main 

DEFINE CLASS Tform As Form 
    Width=350 
    Height=160 
    BorderStyle=2 
    MaxButton=.F. 
    MinButton=.F. 
    Autocenter=.T. 
    Caption="Magnifier" 
    hForm=0 
    hDC=0 
     
    ADD OBJECT chMagnify As CheckBox WITH Value=.F.,; 
    Left=20, Top=20, Autosize=.T., Caption="Activate Magnifier" 

    ADD OBJECT chInvert As CheckBox WITH Value=.F.,; 
    Left=20, Top=56, Autosize=.T., Caption="Invert colors" 
     
    ADD OBJECT lbl1 As Label WITH; 
    Left=190, Top=20, Autosize=.T., Caption="Scale:" 
     
    ADD OBJECT cmbScale As ComboBox WITH Style=2,; 
    Left=240, Top=20, Width=70, Height=21 
     
    ADD OBJECT cmdClose As CommandButton WITH Cancel=.T.,; 
    Left=140, Top=112, Width=70, Height=27, Caption="Close" 

PROCEDURE Init 
    ThisForm.decl 

PROCEDURE Activate 
    IF THIS.hForm = 0 
        THIS.hForm = GetFocus() 
        THIS.hDC = GetDC(THIS.hForm) 
    ENDIF 

PROCEDURE Destroy 
    IF THIS.hDC <> 0 
        = ReleaseDC(THIS.hForm, THIS.hDC) 
    ENDIF 

PROCEDURE cmdClose.Click 
    ThisForm.Release 

PROCEDURE cmbScale.Init 
    WITH THIS 
        .AddItem("Normal") 
        .AddItem("x 2") 
        .AddItem("x 3") 
        .AddItem("x 4") 
        .ListIndex=3 
    ENDWITH 

PROCEDURE MouseMove 
LPARAMETERS nButton, nShift, nXCoord, nYCoord 
    ThisForm.Magnify 

PROCEDURE chMagnify.MouseMove 
LPARAMETERS nButton, nShift, nXCoord, nYCoord 
    ThisForm.Magnify 

PROCEDURE chInvert.MouseMove 
LPARAMETERS nButton, nShift, nXCoord, nYCoord 
    ThisForm.Magnify 

PROCEDURE lbl1.MouseMove 
LPARAMETERS nButton, nShift, nXCoord, nYCoord 
    ThisForm.Magnify 

PROCEDURE cmbScale.MouseMove 
LPARAMETERS nButton, nShift, nXCoord, nYCoord 
    ThisForm.Magnify 

PROCEDURE cmdClose.MouseMove 
LPARAMETERS nButton, nShift, nXCoord, nYCoord 
    ThisForm.Magnify 

PROCEDURE Magnify 
#DEFINE SRCCOPY     0xCC0020 
#DEFINE NOTSRCCOPY  0x00330008 

#DEFINE cnDstWidth  600 
#DEFINE cnDstHeight 140 

    IF ThisForm.chMagnify.Value 
        LOCAL cBuffer, nX, nY, hDstWin, hDstDC,; 
            nMode, nSrcWidth, nSrcHeight, nScale 

        hDstWin = GetActiveWindow() 
        hDstDC = GetWindowDC(hDstWin) 

        cBuffer = Repli(Chr(0), 8) 
        = GetCursorPos(@cBuffer) 
        = ScreenToClient(THIS.hForm, @cBuffer) 

        nX = buf2dword(SUBSTR(cBuffer, 1,4)) 
        nY = buf2dword(SUBSTR(cBuffer, 5,4)) 
         
        nScale = ThisForm.cmbScale.ListIndex 
        nSrcWidth = INT(cnDstWidth/nScale) 
        nSrcHeight = INT(cnDstHeight/nScale) 

        nMode = Iif(ThisForm.chInvert.Value, NOTSRCCOPY,SRCCOPY) 

        = StretchBlt(hDstDC, 10, 100, cnDstWidth, cnDstHeight,; 
            THIS.hDC,; 
            nX-nSrcWidth/2,; 
            nY-nSrcHeight/2,; 
            nSrcWidth, nSrcHeight, nMode) 
         
        ReleaseDC(hDstWin, hDstDC) 
    ENDIF 

PROCEDURE decl 
    DECLARE INTEGER GetActiveWindow IN user32 
    DECLARE INTEGER GetCursorPos IN user32 STRING @lpPoint 
    DECLARE INTEGER GetWindowDC IN user32 INTEGER hwnd 
    DECLARE INTEGER GetDC IN user32 INTEGER hwnd 
    DECLARE INTEGER ReleaseDC IN user32 INTEGER hwnd, INTEGER hdc 
    DECLARE INTEGER ScreenToClient IN user32 INTEGER hWnd, STRING @lpPoint 
    DECLARE INTEGER GetFocus IN user32 

    DECLARE INTEGER StretchBlt IN gdi32; 
        INTEGER hdcDest, INTEGER nXOriginDest, INTEGER nYOriginDest,; 
        INTEGER nWidthDest, INTEGER nHeightDest,; 
        INTEGER hdcSrc, INTEGER nXOriginSrc, INTEGER nYOriginSrc,; 
        INTEGER nWidthSrc, INTEGER nHeightSrc, INTEGER dwRop 
ENDDEFINE 

FUNCTION buf2dword(lcBuffer) 
RETURN Asc(SUBSTR(lcBuffer, 1,1)) + ; 
    BitLShift(Asc(SUBSTR(lcBuffer, 2,1)),  8) +; 
    BitLShift(Asc(SUBSTR(lcBuffer, 3,1)), 16) +; 
    BitLShift(Asc(SUBSTR(lcBuffer, 4,1)), 24)