How To Use Secondary TForm As Screenshot Capture Area?

[webowner47]

Hello,
I'm using the code below to capture desktop screen, but the problem is that the screenshot is taken from the MainForm, and i want to take it from the Secondary TForm instead:

TBitmap* __fastcall TCaptureContainer::CaptureImage()
{
    HDC hdcDesk;
	try
	{
		this->bitbmp->Width  = Screen->Width;
		this->bitbmp->Height = Screen->Height;
		hdcDesk     = GetDC(GetDesktopWindow());
		if ( BitBlt(this->bitbmp->Canvas->Handle, 0, 0, Screen->Width, Screen->Height, hdcDesk, 0, 0, SRCCOPY) ) {
			this->CaptureViewer->Picture->Bitmap = this->bitbmp;
		}
	}
	__finally
	{
		ReleaseDC(GetDesktopWindow(), hdcDesk);
	}
	return this->bitbmp;
}

this is the dynamic TForm with TImage and TTimer:

__fastcall TCaptureContainer::TCaptureContainer()
{
    // Capture Container
	this->CaptureContainer = new TForm(NULL, 0);
	this->CaptureContainer->Parent = NULL;
    this->CaptureContainer->DoubleBuffered = true;
	this->CaptureContainer->BorderStyle = bsSizeable;
	this->CaptureContainer->Position    = poScreenCenter;
	this->CaptureContainer->Width       = 389;
	this->CaptureContainer->Height      = 226;
	this->CaptureContainer->Color       = clBlack;
    this->CaptureContainer->OnClose     = this->CaptureContainerClose;
	this->CaptureContainer->Show();
	// Capture Viewer
	this->CaptureViewer = new TImage(this->CaptureContainer);
	this->CaptureViewer->Parent = this->CaptureContainer;
	this->CaptureViewer->Align  = alClient;
	this->CaptureViewer->Center = true;
	this->CaptureViewer->Show();
	// Capture Streamer
	this->CaptureStreamer = new TTimer(this->CaptureContainer);
	this->CaptureStreamer->Interval = 1;
    this->CaptureStreamer->Enabled  = true;
	this->CaptureStreamer->OnTimer  = this->CaptureStreamerOnTimer;
	// Bitmap
    this->bitbmp = new TBitmap();
}