C++ builder 如何关闭父窗体

C++ builder 怎么关闭父窗体
父窗体调用子窗体的同时，怎么把父窗体关闭，子窗体还保留？是关闭，不是隐藏。求高手解答

[解决办法]
那就是普通的窗体了，
frmlogon 登陆界面
FrmMain 主窗体

C/C++ code

WINAPI WinMain(HINSTANCE, HINSTANCE, LPSTR, int){    try    {         Application->Initialize();         frmlogon = new Tfrmlogon (Application);          frmlogon ->ShowModal();          if( frmlogon ->ModalResult == mrOk )             Application->CreateForm(__classid(TFrmMain), &FrmMain);          delete  frmlogon ;                  Application->Run();    }    catch (Exception &exception)    {         Application->ShowException(&exception);    }    return 0;}