calculating

[cade1980]

Okay I am back, I am looking to learn about calculating fields I can do the adding of 2 fields that are of monetary value but what if I have a table and I have say 10 product keys and the field is "data type text" and every time i use a product key I want the a field that counts down so if i use 4 keys the count field says 6, a key could be "FF100DD" and it would be the same for all 10.

[June7]

That is an aggregate calculation and very different from using two fields or more in an expression.

How it is done depends on your data structure. How do you document the use of a product key?

Do you want to provide project for analysis? Follow instructions at bottom of my post.

[cade1980]

Thanks again I dont know if I am trying to run before I walk but I normally get as much written down and do trial runs before I build my database for real I find I get more info, I have 3 tables for this part one with product info, another with the machine info and a linking table, i have a query that tells me the product name, product key and number of times each different one is used I want to be able to deduct the number used from the total number of keys in the product table sort of to stop me using the product key more times than I am allowed.

so my query tells me: ProductName= Product1 ProductKey= FF100DD CountOfProductKey= 3 and so on for each different product, on a form could I include the CountofProductKey maybe and label it No Of Product Keys Left
Sorry if it is a bit jumbled I dont have much experience actually building forms and stuff but enjoy it.

[June7]

I am a little lost, really need to see structure and some data to test queries.