How to process a query form with CHECKBOX Please help

Dear group,
I am a novice programmer started doing php to process
a query form of my patients.

I have a database and one table in it deals with my
patient information.  Depending on their condition I
divided their age groups into 3 categories. In my
database a table patient_data has a column age_group
and a patient can be any one of young, middle or old
category.
Now the possibility is that a user can selecct 1 or 2
or all three options.

In the query form, I gave the option for a user as a
check box. The piece of html code is as below:

<DIV>Age group</DIV>
<DIV>Young<input type="checkbox" name=""
value=""></DIV>
<DIV>Middle<input type="checkbox" name=""
value=""></DIV>
<DIV>Old<input type="checkbox" name="" value=""></DIV>

Problem:
I want to capture the user options and create an SQL
statement:

Select age_group from patient_data where age_group =
young and old ;


I am truly stuck here. Can any one please help me out
to pass this situation.

Thank you in advance.

Kumar.




__________________________________
Do you Yahoo!?
Yahoo! Mail - You care about security. So do we.
http://promotions.yahoo.com/new_mail