Search in time span relative to date field


I know that it is possible to have relative searches like:
LastUpdated > ‘now - 1 week’

But something like this:
LastUpdated > ‘Started + 5 days’
doesn’t seem to work. It simply gives me all tickets in the results (even if I say … + 100000 days).

So how can I search for tickets, on which the latest update happened more than five days after the “Started” date?

Many thanks in advance.