I'd like a free tool that I can give different pieces of information and have it go and peruse my code base and generate a report. Is there such a tool out there? I'm thinking something along the lines of a spider that can fill in form data (when instructed) and give me the result, and produce a report of what it gets.

The updates script on my webpage is based upon a weblog engine I'm writing, and it's getting large enough where it's hard to test every code path before release.

I'm still unsure as to what your looking to do

If you're having problems with testing your application, then perhaps it's time to look up Test Driven Development (TDD). To give you something in particular, check out SimpleTest.

SimpleTest looks like it will do what I need it to, thanks!