Min cache time ?

I just installed squid 1.0.20 at home and now have a Problem :)

squid uses a % of the age to determine how long it caches some Pages.
It often happens that pages are only cached for about 5 mins.
Is there a possibility to set a 'minimum-cache-time' with the effect
that each page is 'at least' cached for that time ?

CU,
        &TIA
                Sec

P.S.: please CC-Replys since im (not yet) on the list.

-- 
 Jeder Tag an dem du nicht lächelst, ist ein verlorener Tag. (C. Chaplin)
          Hiroshima '45    Tsjernobyl '86   Windows '95
          Black holes are where GOD is dividing by zero