Calculating future Dates in a form to be stored in a table.

[Nosobright]

I am a beginer. I have been tasked at projecting failure dates of Batteries. Batteries have different failure rates. So when we install a battery "Change Date" and the known life is 3 yrs "Failure Time", I need that result to show up in a "Failed" date field. If a battery has a 10 year life, I need that to show up in the Failure Date field.
I cold see an expression in the "failed" field like =([ChangeDate]+[failureTime]) but it does not work. How stupid am I?

[Seth Schrock]

Are the failure rates always in years? If so, what I would do would be to have a Change_Date field and a Failure_Rate field in the table. You would then use a query to calculate the actual failure date. I do it this way because you aren't supposed to store calculated fields (read Database Normalization and Table Structures for the reason).

Your query would work like this:

SELECT Change_Date,
Failure_Rate,
DateAdd("YYYY",Failure_Rate,Change_Date) AS Failure_Time
FROM table_name

You can then base your forms or reports on this query.