Fine if you want to do it in webI then I have a trick, you can either nest everything in a single formula or create intermediate variables.
You already extracted the first part, now use substring function to get the rest of the string. Again put same formula what you used for first part on the rest of the string, in that way you will get the second part. Now again use substring to get the remaining string (number returned by pos function will help you in doing that) and so on, your search will stop when there is no “,” present in your string.