Ralf, I'd gladly help you in this matter but the problem is that at the moment I don't have the time (I'm in the final stages with my master's thesis
)
Until then, I'm afraid you will have to try and sort it out for yourself. To find out about how the search works, you should study the
Code:public function Search($keywords, $url_query, $start_page = 1)
method in the class.Job.php file. I know, it's a monster of a function 
A very quick hack would be to play around in the page_job.php file. The condition
Code:if ($job->Exists() && $job->GetTempStatus() == 0 && $job->GetActiveStatus() == 1)
decides if the job is shown or if a 404 is sent back to Google, for example, in case the job is no longer active. Playing around with the condition might help you on the short term.
PS: this feature request makes very much sense and it should make it into the next jobberbase version, IMHO. I'll think about implementing it in about 1 month.