How to automatically prompt for username/pw when connecting to mapped drive?

Can someone tell me what's wrong with the function below?  I have a user
trying to connect to a mapped network drive accessed through a VPN.  If
my app is the first one that accesses the drive the connection fails.
If they first browse to the drive through Explorer it prompts for the
username and password and then my app can connect without any problems.
  What do I need to change in order to get the username/password prompt?

Thanks,
Craig Peterson
Scooter Software


procedure WNetCheck(Error: DWORD);
begin
if Error <> ERROR_SUCCESS then RaiseLastOSError;
end;

procedure ConnectToShare(const AShare: string);
var
   S: string;
   NetResource: TNetResource;
   RemoteName: array [0..MAX_PATH] of char;
   RemoteLen: DWORD;
   Error: DWord;
begin
   // Don't do anything for local drives and drives already connected
   if Length(AShare) = 2 then
   begin
    S := IncludeTrailingPathDelimiter(AShare);
    if (GetDriveType(PChar(S)) <> DRIVE_REMOTE) or
       DirectoryExists(S) then
      Exit;
   end
   else if DirectoryExists(AShare) then
     Exit;

   FillChar(NetResource, SizeOf(TNetResource), 0);
   NetResource.dwType := RESOURCETYPE_DISK;

   // If it's a mapped drive retrieve the remote path to connect to
   if Length(AShare) = 2 then
   begin
    RemoteLen := MAX_PATH;
    WNetCheck(WNetGetConnection(PChar(AShare), RemoteName,
              RemoteLen));
    NetResource.lpLocalName := PChar(AShare);
    NetResource.lpRemoteName := RemoteName;
   end
   else
     NetResource.lpRemoteName := PChar(AShare);

   Error := WNetAddConnection3(Application.Handle, NetResource, nil, nil,
     CONNECT_INTERACTIVE);

   // If the connection is already open but the DirectoryExists failed
   // above,  try killing the existing connection and connect again
   if (Error = ERROR_ALREADY_ASSIGNED) or
      (Error = ERROR_DEVICE_ALREADY_REMEMBERED) then
   begin
    WNetCancelConnection2(NetResource.lpLocalName, 0, false);
    Error := WNetAddConnection3(Application.Handle, NetResource,
      nil, nil, CONNECT_INTERACTIVE);
   end;
   WNetCheck(Error);
end;