Pre-defined filters plus filter menu

A question I have asked for some time now and yet to see anyone address this.

FILTERS

We have a great feature built in that allows us to pre-define specific filters for set parameters and it works a treat. BUT we need to be able to go that one step further to interrogate the database within the initial subset that the pre-defined filters gives us.

Best explained with our specifics.
It is a database of some 25,000 soldiers from WWII. The information contained on the file is birth enlistment, death dates and locations, awards, unit, rank, prisoner of war dates and camps etc etc
We have A thru Z filter buttons
We have Qualified, Not Qualified, Unconfirmed STATUS Filter Buttons.

What we need though is the ability to say work within a specific group (such as the Qualified soldiers only and enter further search parameters such as a range of dates for death (1940 to 1945).

Our researchers are not as computer literate as I would like but thats the way things are. Trying to teach them to enter multiple parameters for a search criteria is always an option BUT THAT LOSES THE QUICK FILTERS pre programmed as mentioned above.

They therefore have to remember to add the initial criteria to establish the first subset of data (i.e qualified, not qualified) every time they "lose the criteria which seems to happen if you perform certain functions whilst working on records i.e it reverts back to the beginning with no filters applied at all).

So what would be ideal (and surely is not that hard ? ) is to allow the filter menu to also be applied to pre-filtered record set ?

Only other option is to work out which are the most valuable top level selections and create separate screens and menu items for each. Grrrrrrr

SELECT ONLY QUALFIED RECORDS and have no pre-defined filters
SELECT ONLY NON QUALIFIED RECORDS and have no pre-defined filters
SELECT ONLY UNCONFIRMED RECORDS and have no pre-defined filters