A:  Note:  The reason that you want to be able to lock a directory is that if you want to place data files on to a CD and read them there, you need a directory lock so that the BDE knows to not try to write to that directory.  This makes the files read only, but it works.

unit Dirlocku;

interface

uses
  SysUtils, WinTypes, WinProcs, Messages, Classes, Graphics, Controls,
  Forms, Dialogs, DbiTypes, DbiProcs, DbiErrs, DB, StdCtrls, Buttons,
  FileCtrl;

type
  TForm1 = class(TForm)
    Database1: TDatabase;
    Button1: TButton;
    Button2: TButton;
    Edit1: TEdit;
    Label1: TLabel;
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
  private
    function ChkPath : Boolean;
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.DFM}

function TForm1.ChkPath : Boolean;
var
  s : String;
begin
  If DirectoryExists(Edit1.Text) then
    with DataBase1 do begin
      Connected := False;
      Params.Add('Path=' + Edit1.Text);
      Connected := TRUE;
      Result := TRUE;
    end
  else begin
    s := 'Directory : ' + Edit1.text + ' Does Not Exist';
    Application.MessageBox(pChar(s), 'Error!', MB_ICONSTOP);
    Result := FALSE;
  end;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  if ChkPath then
    check(DBIRelPersistTableLock(Database1.Handle, 'PARADOX.DRO', 'PARADOX'));
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
  if ChkPath then
    check(DBIAcqPersistTableLock(Database1.Handle, 'PARADOX.DRO','PARADOX'));
end;

end.