htaccess: Get files from another directory

[eluser]codex[/eluser]
What I'm trying to achieve is that files called via

Code:

http://www.domain.com/files/

are being served from the real directory

Code:

http://www.domain.com/assets/files/whatever/blah/

In my htaccess I have this

Code:

RewriteRule ^http://www.domain.com/files/$ http://www.domain.com/assets/files/whatever/blah/

but that doesn't work. Am I doing something wrong here or is it just not possible?