try this custom item:

 

class CCustomItemIPAddress : public CXTPPropertyGridItem
{
 class CInplaceEditIPAddress : public CXTPPropertyGridInplaceEdit
 {
 public:
  BOOL Create(LPCTSTR lpszClassName, LPCTSTR lpszWindowName, DWORD dwStyle, const RECT& rect, CWnd* pParentWnd, UINT nID, CCreateContext* pContext)
  {  
   if (!CWnd::Create(WC_IPADDRESS, lpszWindowName, dwStyle, rect, pParentWnd, nID, pContext))
    return FALSE;
   
   ModifyStyle(WS_BORDER, 0);
   ModifyStyleEx(WS_EX_CLIENTEDGE, 0, SWP_FRAMECHANGED);  
   return TRUE;
  }
 };

public:
 CCustomItemIPAddress::CCustomItemIPAddress(CString strCaption)
  : CXTPPropertyGridItem(strCaption)
 {
 }

protected:
 virtual CXTPPropertyGridInplaceEdit& GetInplaceEdit()
 {
  return m_wndEdit;
 }

private:
 CInplaceEditIPAddress m_wndEdit;

};