.ht access using document.referer?

[forrich]

I need every page of my site to be redirected to my main page, but only when referred from outside the site. I am sceptical about using 'document referer' because of s/e problems.

How can I use an .ht access file to do this? would this work...

redirect /mysite_directory/ http://mysite_directory/index.htm

Any other ideas please?

Thanks Richard