How to remove the border of CTXReBar

I created a CTXReBar m_wndReBar by following codes:

 DWORD dwCtrlStyle = TBSTYLE_FLAT;
 DWORD dwStyle = WS_CHILD | WS_VISIBLE | CBRS_TOP | CBRS_GRIPPER | CBRS_TOOLTIPS | CBRS_FLYBY | CBRS_SIZE_DYNAMIC;

 if (!m_wndReBar.Create(this,  dwCtrlStyle, dwStyle)) {
  AfxMessageBox("Can not create Rebar\n");
  return -1;      // δÄÜ´´½¨
 }
 m_wndReBar.AddBar(&m_wndDlgBar, _T("BenYuan"), NULL, RBBS_NOGRIPPER);

The rebar always has 3d boders, how can I remove the borders? Thanks.