SEO dynamic page indexed but page doens't exist anymore

[vwennink]

Hi,
I'm building a dynamic site with search engine friendly url's in it. What do I have to do when a dynamic productpage is indexed by a search engine and the product doens't exist anymore.
The problem is that the productpage is embedded in a mainpage. I already have made a custom 404 page but I don't know if it works. In the code I detect if a product exists, if not, I use a META HTTP-EQUIV=Refresh 0sec to a fake url(in the same domain). Then the 404 page will be shown. I wonder if the search engines will take this productpage out of the index. This is exactly what I want.
Does someone have the answer to this or is there a better solution?

[tbear]

Would it not be possible to create a page explaining that the product does not exist any more and referring the visitor to current products as alternatives. Thus offering the visitor an alternative.
Obviously depends on your products.....

[vwennink]

Yes, I do that with the customised 404 error page, refering to the sitemap. My goal is to get my productpage out of the search engine index, without losing my overall position in de search engines. If you have 100 products in the search engines, and they do not exist anymore, it's not good that they will all point to the sitemap.