SharePoint 2010 list logic calculated column

Question

I need to record number of points for each seminar attended [points received] and the points remaining [points remaining].

For example, for attending each seminar I get 2 points and the total number of points to receive is 15. So after I attend one seminar, I have 13 points remaining, after I attend the 2nd seminar, I have 11 points remaining, etc.

Is it possible to have a calculated column in SharePoint list to display this information? I tried the following formula for the points remaining = 15 - [points received], but it always gives me 13 points in the [points remaining] column.

I also tried = [points remaining] - [points received], this gives me an error:

"The formula contains a circular reference (the calculated column refers to itself)."

Could you please provide any suggestions? If a calculated column is not an option here, what else I could use to achieve the task of recording this information in a list?

Thank you in advance.

Answer 1

If you familiar with programming you can have a look on Event Receivers.
Here you have instructions how to implement such receiver.

Answer 2

I think the main problem you will have are the states you described with the increment of a course. The column calculation doesn't work with different states as far as I know.

You could either use a workflow that starts on the modification of the points received column and manipulates the required value of [points remaining].

The other option would be a JavaScript file added to the EditForm via the Content-Editor Webpart of the List that would take care of the logic while editing the list values.