Regarding your sentence, my first question is: What exactly is this?
Since you appear to be asking for some specific assistance, why not be as specific as you can in your request? i.e., "this problem about ____...", "this essay (or thesis), with a special focus on ______ ...", etc.
Even though you may have already made previous reference to whatever this is, your request for assistance will be made stronger by being as specific as you can be here. With this suggestion in mind, you might consider this rephrasing:
"I welcome comments and feedback concerning _________ (fill in the blank here, being as explicit as you can) from any of those who will not be available during the upcoming webinar to be held _________ (fill in the blank with the date/from time - to time) at (URL)."
Student or Learner