Handbrake comes with a Command Line program (default path = C:\Program Files\HandBrake\HandBrakeCLI.exe)
That would probably be your best bet versus trying to make a macro to interact with the GUI version of Handbrake. If you only wanted to do one at a time a simple DOS batch script would allow you to drag and drop files:
1) Open Notepad
2) Paste the following text:
"C:\Program Files\HandBrake\HandBrakeCLI.exe" -i %1 -o %1.mp4 -e x264 -b 2000 -B 128 -X 480
3) Save the file as HandbrakeCLI.bat (or anything else you want as long as it ends in .bat)
4) Place that where the video you want to convert is located and drag the video file onto the .bat file. A DOS window should pop up and start converting the video.