delphi 数据筛选问题

例如得知
http://www.baidu.com/abc/123.doc ## !@#$%^&*()_
如何把123.doc筛选出来

呵呵..这个问题有点难度多给点分希望能....
补充一下:
http://www.baidu.com/aabc/12aaa3.doc ## !341234
http://www.baidu.com/abaaaaaaaaaaaaaaaaaaad/1a32.doc ## !4324234
http://www.baidu.com/aaaabe/15aaaaaaa5.doc ## !213^&*1

把里面的doc文件都筛选出来的方法

刚有点错误 ，不好意思 现在修正了

unit Unit1;
interface
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls;
type
TForm1 = class(TForm)
Edit1: TEdit;
Edit2: TEdit;
Button1: TButton;
procedure Button1Click(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;
var
Form1: TForm1;
implementation
{$R *.dfm}
function LastPos(const subStr, s:string):integer;
var
iPos:Integer;
strTmp:Widestring;
begin
Result:=0;
strTmp:=s;
iPos:=Pos(SubStr,strTmp);
while iPos<>0 do
begin
//删除已经查找过的字符
Delete(strTmp,1,iPos+Length(SubStr)-1);
Result:=Result+iPos;
iPos:=Pos(SubStr,strTmp);
if iPos=0 then Break;
Result:=Result+Length(SubStr)-1;
end;
end;
procedure TForm1.Button1Click(Sender: TObject);