Finding a missing number

I am doing a survey of a group of people for a special demographic research. I need to find what age is missing from this group.

For example, my report current display as follows for year 2013

White
17
18
20
21Black
18
19
22
25Asian
20
21
22
23Prefer Not to Answer
20
21
23
24

I have 2 parameter field which have values ranging from ages 18-30 and year 2012 -2014.

I need a forumal that will display the group of people who's age I have not researched.

Need Example data:

Parameter searching for: age 19 and year 2013

White
17
18
20
21


Asian
20
21
22
23


Prefer Not to Answer
20
21
23
24 

I will need White, Asian, and Prefer not to answer group of people research.

How can I do this? I am kind of new to crystal reports.