How to draw on an unfilled box on a video stream using the mouse

Hi,

I am using dshownet(first time) and C#. I have got a sample to take the web cam input and display it on a form. I now need to draw a rectangle on top of the video stream using the mouse. (the intent is to track what is inside the box from there onwards).

I heard that there is something called VMR. So I went to the dshownet samples and went through them. I didnt find any samples that use the mouse to overlay a shape on the video stream. Someone on here suggested to use colorkey. Another person said to use GDI+ and mouse handling. I tried to compile the DXLogo sample but got this error :
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Error 1 Cannot create an instance of the abstract class or interface 'System.Drawing.Image' C:\Documents and Settings\TLNA\Desktop\Final Year Project\Libraries\DirectShow library 2\DirectShowSamples-2010-February\Samples\Capture\DxLogo\Capture.cs 128 32 DxLogo-2008

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for the code section:
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if (fileName.Length > 0)
{
m_Bitmap = new Image(fileName); // error happened here

Rectangle r = new Rectangle(0, 0, m_Bitmap.Width, m_Bitmap.Height);
m_bmdLogo = m_Bitmap.LockBits(r, ImageLockMode.ReadOnly, PixelFormat.Format24bppRgb);
}

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I know that I must go through the IMVRMixerBitmap9 Interface. But I really dont know where to start. Should I read the Directshow API docs.

btw I also have the book Programming Microsoft Directshow for digital video and television. I started reading that book and stopped after a few pages since the code is mainly in C++. Should I continue to read this is book ? How can I accomplish the certain mentioned tasks in C# ?

Any suggestions as how to draw on the video. Some useful links(tutorials) would be helpful.

Many Thanks
Tlna