delphi Get and compare big text file from web with string - delphi

Question

I have one big text file with 95000+ lines on web
Now for example:
I have one string
I want to match that string in that file
and read that whole line where that string is placed in file
I am using wininet
I can load whole file in to string
but while matching it takes alot of time and gui hangs
is there anyway to do it more faster ?
edit:
Here is code i m using to get urlcontents from web
in button1
var
s:string;
begin
//1- as file is big it takes alot of time :/
S := GetUrlContent('web url example');
if (Pos('string i want to search', s)> 0) then
begin
mmo1.lines.add('Found');
//2- now how can i show extact line that contains string
end;
end;
//----------------------------------------------------
function GetUrlContent(const Url: string): string;
var
NetHandle: HINTERNET;
UrlHandle: HINTERNET;
Buffer: array[0..1024] of Char;
BytesRead: dWord;
begin
Result := '';
NetHandle := InternetOpen('Delphi 5.x', INTERNET_OPEN_TYPE_PRECONFIG, nil, nil, 0);
if Assigned(NetHandle) then
begin
UrlHandle := InternetOpenUrl(NetHandle, PChar(Url), nil, 0, INTERNET_FLAG_RELOAD, 0);
if Assigned(UrlHandle) then
{ UrlHandle valid? Proceed with download }
begin
FillChar(Buffer, SizeOf(Buffer), 0);
repeat
Result := Result + Buffer;
FillChar(Buffer, SizeOf(Buffer), 0);
InternetReadFile(UrlHandle, #Buffer, SizeOf(Buffer), BytesRead);
until BytesRead = 0;
InternetCloseHandle(UrlHandle);
end
else
{ UrlHandle is not valid. Raise an exception. }
raise Exception.CreateFmt('Cannot open URL %s', [Url]);
InternetCloseHandle(NetHandle);
end
else
{ NetHandle is not valid. Raise an exception }
raise Exception.Create('Unable to initialize');
end;