Make BOLD without tags

I have a form where a user inputs information in a TEXTAREA. But I want to give the user the option to make BOLD or ITALICS only part of the text. Just like in Yahoo! mail or Hotmail, you know, how you can click on the “B” icon and it BOLDS what’s highlighted.

Can I do that? Im using PHP and MySQL.

Also, how can a be automatically converted into a link?

Thanks in advance,