Let's see if I have this correct:
You have a blog at myblogdomain.com which you want to move to TypePad with domain mapping so it shows up at the same domain. You have a few posts on your old blog (myblogdomain.com/this_is_a_post.html, for example) which you'd like to redirect to the new TypePad link (myblogdomain.com/2008/06/this-is-a-post.html, for example).
The easiest way to accomplish this is to use the TypePad file manager to create html files at the locations of your old posts with meta redirect tags that point to the new location. You'd have to create a new html file for each post url you want to redirect.
According to this site, both google and yahoo will accept a meta redirect with zero delay as equivalent to a 301 redirect, which will make sure that these search engines follow your links to their new (hopefully permanent!) locations on your TypePad blog.
I've glossed over a lot of the details here, so please let me know if this is sufficient or if you need some additional help!