Let me understand you.
Search function on a wp blog and if someone searches for something not on the blog, they do go to an error page.
What you want to do is if someone searches for something not found, instead to go to a page you select?
There is a way, but for the life of me right now I can not think of it! LOL
It is only good to send searches to one page only.
And if memory serves me correctly, if not done right, all searches will go to the same page.
Now let me hunt down the correct information you need.