Don't leave any further comments. As you mention it's been done already and hasn't helped.
Flag one of the answers for moderator attention, use the Other reason and explain that the user is persistently promoting his youtube channel in a spammy way. The mod will then action the flag and determine the appropriate course of action, which may be a mod message to the user and/or a short ban.
Using a valid blog entry or external link to support your answer like he has here is fine provided you are open when it is your own blog (text like "check out my blog post which explains the answer more fully" would be satisfactory), although it is preferred that he excerpts sufficient material from the supporting external post for the answer to make sense - IOW the answer shouldn't be just a link.
Straight out promotional links like this one are deemed spam and must be stamped on. It would seem that this user's primary purpose here is to promote his youtube channel using the guise of answering questions - like no-one has tried that before!! Sucks to be him though because all new users have a
rel=nofollow inserted into their links, as you can see from this snippet from his surviving answer with a link:
<a href="http://www.mrexcel.com/forum/excel-questions/611558-visual-basic-applications-create-unique-list-range-data.html" rel="nofollow">Create Unique list</a><br>
<a href="http://www.ozgrid.com/forum/showthread.php?t=40545" rel="nofollow">Create Unique list 2</a></p>