[For Windows Users]
The script works for about 25-35 files at a time. Basically, the script will do all the mouseclicks required to upload files for you.
Install autohotkey http://www.autohotkey.com/
Download the script and rename the .txt file to .ahk (autohotkey file extension) http://codepad.org/YAQiaIj6 There is some information about how the code works in the file.
Get an image of the memrise upload button and name it upload.bmp Screenshot + paint + save to .bmp should do the trick. For example, Make sure you place this file in the same folder as the upload script. The script works by finding the upload button and clicking on it for you.
Upload the first audio file to your level. This is to set the default directory for selecting audio files.
Double click the script to launch it. Then press Ctrl + D whenever you want to batch upload. Tip zoom out to 33% to make sure all the entries in a level are visible on your screen.
Write the filename in the dialogue box that pops up. You only need to do this once.
The script upload the files for you.
Make sure your files are named uniformly (Ex: sample-01.mp3, sample-02.mp3, ...).