Hi... There is not a direct way to do this without modifying the source code or having a separate application run to handle this.
I would suggest...
1. Setup an instance of Dynamic Forms and request the subject line, personalized newlsetter, etc... So basically you would be duplicating the form where you create a newsletter at.
2. Create a SQL Completion event that would add the records to the appropriate Opt In Email tables to send out a newsletter
3. Create a SQL Completion event to insert the information directly into the blog.
This way you wouldn't have to modify the source directly but you could still implement what you need. You would still need to make sure you inserted these into the correct tables and so forth to keep referential integrity etc...
If you were to have us do this it would fit into a range of 6-8 Premium Support hours. If you wanted to go that route you could pick up the hours at
http://www.datasprings.com/Premium-Support. Thanks,
Chad