user urlmon,wininet; 
procedure qiehuanproxy(const proxyname:string); 
var info:TInternetProxyInfo; 
 lngth:integer; 
 h:integer; 
 proxy :pChar; 
 bypass :PChar; 
 begin 
 proxy:=pchar(proxyname);//proxy address:port 
 bypass:=pChar(''); 
 info.dwAccessType := INTERNET_OPEN_TYPE_PROXY  ; 
 info.lpszProxy :=proxy; 
 info.lpszProxyBypass:=bypass; 
 lngth:=sizeof(info); 
  h:=UrlMkSetSessionOption(INTERNET_OPTION_PROXY ,@info,lngth,0); 
end;