It's not a good idea to use calculations in tables.
I can see where you are coming from, but bear in mind, that a computer is designed to complete calculations and therefore storing a value is not needed.
I'm not sure if I am making sense, so let me show you:
You have a table with personal contacts on it. On this table, there is no need to have both a persons date of birth and their age. The two are related to each other.
If I said that "George" was born on the 01/01/1900, you would automatically know that George was 103. I would not need to tell you that George was 103.
In the same way, you can keep base data on a table, but use a query or VBA (code) to complete the calculatioin when you need it.
Hope this helps.
Fitz