如何在delphi里用代码实现创建VPN连接?

我的代码如下,怎么总提示连不成功:
type
  GUID = record //申明调用RAS（创建VPN连接用）函数所需结构体
  Data1: integer;
  Data2: Shortint;
  Data3: Shortint;
  Data4: array[0..6] of byte;
end;

type
  RASIPADDR = record //申明调用RAS（创建VPN连接用）函数所需结构体
  a: byte;
  b: byte;
  c: byte;
  d: byte;
end;

type
  RASENTRY = record //申明调用RAS（创建VPN连接用）函数所需结构体
  dwSize: integer;
  dwfOptions: integer;
  dwCountryID: integer;
  dwCountryCode: integer;
  szAreaCode: array[0..9] of byte;
  //szLocalPhoneNumber: array[0..127] of byte;
  dwAlternateOffset: integer;
  ipaddr: RASIPADDR;
  ipaddrDns: RASIPADDR;
  ipaddrDnsAlt: RASIPADDR;
  ipaddrWins: RASIPADDR;
  ipaddrWinsAlt: RASIPADDR;
  dwFrameSize: integer;
  dwfNetProtocols: integer;
  dwFramingProtocol: integer;
  szScript: array[0..258] of char;
  szAutodialDll: array[0..258] of char;
  szAutodialFunc: array[0..258] of char;
  szDeviceType: array[0..15] of char;
  szDeviceName: array[0..127] of char;
  szX25PadType: array[0..31] of char;
  szX25Address: array[0..199] o