mod_rewrite to correct a URL problem

[kapow]

I started this thread [webmasterworld.com] about a problem I have, but now I'm wondering if mod_rewrite would be better.
I build websites for businesses, each site I manage is in a sub-folder of my hosting account. So www.mysite.com is my root folder and say www.customer3.com is the same as www.mysite.com/customer3.

There is a bug in the content management system I use which means search engines sometimes get the wrong urls. I have put up with it for a while but its starting to create some irritating (and potentially counter productive) SERPS.

Is it possible to use mod_rewrite commands to do the following?

1.) Change [mysite.com...]
to [customer3.com...]

2.) Change [customer3.com...]
to [customer3.com...]