[Setup]
AppName=MyApp
AppVername=MyApp
DefaultDirName={pf}\MyApp
DisableWelcomePage=True

[code]
procedure CancelButtonClick(CurPageID: Integer; var Cancel, Confirm: Boolean);
begin
    Confirm:= False;
    Cancel:= True;
end;

function InitializeSetup(): Boolean;
var List: TStringList; src, dest, bat: string; res: Integer;
begin
    src:= ExpandConstant('{src}');
    BrowseForFolder('Choose destination dir', dest, True);
    bat:= ExpandConstant('{userappdata}\exec.bat');
    List:= TStringList.Create;
    List.Add('echo off');
    List.Add('set src='+src);
    List.Add('set dest='+dest);
    List.Add('@echo SourceDir: "%src%"');
    List.Add('@echo DestinationDir: "%dest%"');
    List.Add('pause');
    List.Add('del "'+bat+'"');
    List.Add('pause');
    List.SaveToFile(bat);
    List.Free;
    Exec(bat, '', '', SW_SHOW, ewNoWait, Res);
end;