set single selection style:
DWORD style = GetWindowLong(m_hWnd,GWL_STYLE);
SetWindowLong(m_hWnd,GWL_STYLE,style | LVS_SINGLESEL);
set multi selection style:
DWORD style = GetWindowLong(m_hWnd,GWL_STYLE);
SetWindowLong(m_hWnd,GWL_STYLE,style & ~LVS_SINGLESEL);