如何去掉按钮在输入焦点切换时所产生的闪烁

HBRUSH CcsDlg::OnCtlColor(CDC* pDC, CWnd* pWnd, UINT nCtlColor)
{
HBRUSH hbr = CDialog::OnCtlColor(pDC, pWnd, nCtlColor);

// TODO:  Change any attributes of the DC here
if(nCtlColor == CTLCOLOR_BTN)
{
hbr = (HBRUSH)GetStockObject(NULL_BRUSH);
}
// TODO:  Return a different brush if the default is not desired
return hbr;
}