Hi, I draw a ruler in the screen and now I want to make a cursor "run" through this ruler. But when I use a for loop to do this, it makes the cursor but doesn't erase the previous drawn one. The code I'm using to do this is above. Can anybody help me? The code follows:

void CCompass::DrawCompass(CRect *pRect, CDC *pDCa)
{
//
// Get DC if no DC is passed
//
CDC *pDC = pDCa;
if(pDCa == NULL) pDC = GetDC();

//
// Create temporary work DC (memory DC) and bitmap
//
CDC dcMem;
CDC dcOriginalMem;
int IniDC;
CBitmap bmTemp;
dcMem.CreateCompatibleDC(pDC);
dcOriginalMem.CreateCompatibleDC(pDC);
bmTemp.CreateCompatibleBitmap( pDC,pRect->Width(),pRect->Height() );
CBitmap *pbmOld = dcMem.SelectObject(&bmTemp);
dcOriginalMem.SelectObject(&bmTemp);
CRect rect = *pRect;

//
// Draw background rectangle
//
CBrush WorkSpaceBrush( RGB(255, 255, 255));//GetSysColor( COLOR_BTNFACE ) );
CBrush *pOldBrush = dcMem.SelectObject(&WorkSpaceBrush);
dcOriginalMem.SelectObject(&WorkSpaceBrush);
CPen *pOldPen = (CPen *)dcMem.SelectStockObject( NULL_PEN );
dcOriginalMem.SelectStockObject( NULL_PEN );
dcMem.Rectangle(&rect);
dcOriginalMem.Rectangle(&rect);
dcMem.Draw3dRect(&rect,(COLORREF)GetSysColor(COLOR_3DSHADOW),
(COLORREF)GetSysColor(COLOR_3DHILIGHT));
dcOriginalMem.Draw3dRect(&rect,(COLORREF)GetSysColor(COLOR_3DSHADOW),
(COLORREF)GetSysColor(COLOR_3DHILIGHT));
dcMem.SelectStockObject( BLACK_PEN);
dcOriginalMem.SelectStockObject( BLACK_PEN);

//
// Create rgn
//
rect.InflateRect(-1,0);
CRgn rgnRect;
rgnRect.CreateRectRgn(rect.left,rect.top,rect.right,rect.bottom);
dcMem.SelectClipRgn(&rgnRect);
dcOriginalMem.SelectClipRgn(&rgnRect);
rect = *pRect;
rect.InflateRect(30,0);

//
// Calculate some ratios
//
float fDegreePerDeltaPixel = (float)rect.Width()/(float)DEGREES_IN_VIEW;
if((int)fDegreePerDeltaPixel < 2) fDegreePerDeltaPixel = 2.0;

//
// Calculate most left degree point
//
int nStartDegree = (int)m_fHeading - rect.Width()/2 / (int)fDegreePerDeltaPixel;

//
// If nStartDegree is < 0 or > 360, adjust to reflect a valid compass heading
//
if( nStartDegree < 0 ) nStartDegree = 360 + (nStartDegree % 360);
else if( nStartDegree > 360 ) nStartDegree %= 360;

//
// Create a font and set color
//
CFont cFont,*cpOldFont;
cFont.CreatePointFont(70,_T("Arial"));
cpOldFont = (CFont *)dcMem.SelectObject(&cFont);
dcOriginalMem.SelectObject(&cFont);
COLORREF crOldBkColor = dcMem.SetBkColor( GetSysColor( COLOR_BTNFACE ) );
dcOriginalMem.SetBkColor( GetSysColor( COLOR_BTNFACE ) );
TEXTMETRIC tm;
dcMem.GetTextMetrics(&tm);
dcOriginalMem.GetTextMetrics(&tm);

//
// Draw compass
//
int nTextYPosition;
UINT y;
int numDivisions = 0;
for(int i = 0; i < rect.Width(); i += (int)fDegreePerDeltaPixel)
{
//
// Calculate height of tick mark amd draw it. This is based on the
// m_wTicAlign flag.

if( (nStartDegree % 10) == 0)
y = rect.bottom - rect.Height()/2;
else if( (nStartDegree % 5) == 0)
y = rect.bottom - rect.Height()/3;
else
y = rect.bottom - rect.Height()/5;
dcMem.MoveTo(rect.left+i,rect.bottom-1);
dcOriginalMem.MoveTo(rect.left+i,rect.bottom-1);
dcMem.LineTo(rect.left+i,y);
dcOriginalMem.LineTo(rect.left+i,y);
nTextYPosition = rect.Height()/2 - tm.tmHeight;

// Draw text
//
if( (nStartDegree % 15) == 0)
{
CString s;
switch(nStartDegree)
{
case 0 : s = _T("N") ; break;
case 45 : s = _T("NE"); break;
case 90 : s = _T("E") ; break;
case 135: s = _T("SE"); break;
case 180: s = _T("S") ; break;
case 225: s = _T("SW"); break;
case 270: s = _T("W") ; break;
case 315: s = _T("NW"); break;
default: s.Format(_T("%d"),nStartDegree); break;
}

dcMem.ExtTextOut(
rect.left+i-dcMem.GetTextExtent(s).cx/2,
nTextYPosition,
ETO_OPAQUE,
NULL,
s,
NULL
);
dcOriginalMem.ExtTextOut(
rect.left+i-dcMem.GetTextExtent(s).cx/2,
nTextYPosition,
ETO_OPAQUE,
NULL,
s,
NULL
);
}
/*
//
// Wrap around
//
if(++nStartDegree >= 360) nStartDegree = 0; */
}

//
// Draw center line
//
CPen MarkerPen( PS_SOLID, 1, RGB(100, 200, 200) );
dcMem.SelectObject( &MarkerPen );
dcOriginalMem.SelectObject( &MarkerPen );

// This code doesn't belong to here... only from Draw center line ... or maybe it belongs
// Create a copy of the original ruler, so that we can redraw it before altering the cursor position
IniDC = dcMem.SaveDC();
dcOriginalMem.BitBlt(0, 0, rect.Width(), rect.Height(), &dcMem, 1, 0, SRCCOPY);

for (int j = rect.left; j <= rect.right; j++)
{
// Create a copy of the original ruler, so that we can redraw it before altering the cursor position
dcMem.RestoreDC(IniDC);
dcMem.BitBlt(0,0,rect.Width(),rect.Height(),&dcOriginalMem,0,0,SRCCOPY);

/*wait*/for(int k = 0; k<1000000; k++);

Pump();
dcMem.MoveTo(j, rect.top);
dcMem.LineTo(j, rect.bottom);
Invalidate();
pDC->BitBlt(0,0,rect.Width(),rect.Height(),&dcMem,0,0,SRCCOPY);
}
//int cx = rect.left+(rect.Width()/2 / (int)fDegreePerDeltaPixel) * (int)fDegreePerDeltaPixel;
//dcMem.MoveTo( cx,rect.top);
//dcMem.LineTo( cx,rect.bottom);
//pDC->BitBlt(0,0,rect.Width(),rect.Height(),&dcMem,0,0,SRCCOPY);

//
// finally draw to screen from temperary dc
//
// pDC->BitBlt(0,0,rect.Width(),rect.Height(),&dcOriginalMem,0,0,SRCCOPY);

///////////////////////////////////////////////////////////////////////////
pDC->SelectClipRgn(NULL);
rgnRect.DeleteObject();
dcOriginalMem.SelectObject(pOldBrush);
WorkSpaceBrush.DeleteObject();
dcOriginalMem.SetBkColor( crOldBkColor );
dcOriginalMem.SelectObject(pbmOld);
bmTemp.DeleteObject();
dcOriginalMem.SelectObject(cpOldFont);
cFont.DeleteObject();
dcOriginalMem.SelectObject(pOldPen);

dcOriginalMem.SelectObject(cpOldFont);

///////////////////////////////////////////////////////////////////////////
if(pDCa == NULL) ReleaseDC(pDC);
}