Passing CString with SendMessage

pass pointer of CString in wParam or lParam parameters

in thread
CString * myString = new CString(L"BLANK");
AfxGetMainWnd()->SendMessage(WM_USER_THREAD_REPLACE,(WPARAM)myString, 0);

in window procedure
LRESULT CChildView::OnThreadReplace(WPARAM wParam, LPARAM lParam)
{
   CString * string1 = (CString *) wParam;
   Invalidate();
   return 0;
}