How to issue a proper 404 AND show page content

[npd1164 Profile]

in Apache mod rewrite, I use the command in an htaccess file:
ErrorDocument 404 http://www.somesite.com/customerrorpage.htm
(issues both a 404 AND delivers some basic page content to the user)

However, a number of my clients use a host running windows servers and isapi rewrite ver. 2.x

Is there a way to achieve the same as the above with Isapi Rewrite 2.x?

[npd1164 Profile]

Okay, forget my posted question!

Beyond the fact the original post's example code included an absolute path where it should be root relative, I'm abandoning the idea of using it as it does not do what i want or thought it did.