How can i extract a field from a struct based on some condition?

I have two structs containg fields eg. id which is 'time of arrival' and id_allocated which is 'id to which an organ was allocated to' and blood group of donor and reciever.

I want to check who got allocated in year 1, year 2 and so on, which I am able to accomplish. My problem is to find the allocation time according to bloodgroup. I am not able to make separate struts based on bloodgroup.

[Sindar]

It sounds like tables would work better than structs here.

But, if you are set on a struct, give us more info on it's structure (heh). Probably you can just copy the command line summaries