Cut out part of a Bitmap in C#

I am looking for someone who is expert in bitmap manipulation. This project is sort of like cropping a Bitmap but reversed. In cropping you specify a rectangular area on the image and throw away the rest of the image. In this case, I want to throw away the rectangular area and keep the rest of the image. So there will be a blank area in the middle of the image. The cut out area can be any where on the image. The cut out area cannot be white or black. It has to be transparent. So if there is a background image, the background image will show through the cut out. You should probably generate a static class for this. The inputs will be the cut out window size, the top left corner location of the cut out and the Bitmap image. The output will be the Bitmap image with part of it cut out.. This will be incorporated in my code. My code is executed in real time and the bitmap image is updated continuously with different cut outs. Therefore, the way you do the cutout must be the most efficient way so there isn't much lag. I have attempted this myself and I ended up with slow running code which wasn't suitable for a real time app. Since my app is timing sensitive, I will need your source code to try before I award you the project and make payment. My budget for this project is $30. For someone who is familiar with bitmap manipulations, this will be a 15 minute job. This is urgent and I need it done right away.