I have form contains 4 Fields ( 2 drop-down box ,2 Fields)

1- sex : ALL,MALE,FEMALE
2-agemin --->minimum age
3-agemax--->maximum age
4-country:ALL,USA,UK,FRANCE,ITALY

how to make query that when for example I select
sex : ALL
agemin: 10
agemax:14
country: USA

the result will be all male and female profiles in USA between 10 and 14 (10,11,12,13,14)

the difficult thing is how to setup ALL so when you select ALL will give you everything in that field either sex or country .
if I select ALL in country will give me all people from USA,UK,FRANCE AND ITALY

how can I do that and setup the "all".

thanks in advance