Example : Record 1 , Field A = 100 -- Record 2 , Field A = 80 How do I create a field which shows total of 180 adding the 2 fields which are the same (A) but in different records. thanks

FMP 5 doesn't have custom functions. What you need to use is the Sum function with a relationship that will include all the desired records. It will look like this: Sum (Relationship name::Field A)

I am rather new at Filemaker could you elaborate how I make a relationship -thank you

In the File menu you will find Define Relationships. Select that and you will get a dialog box, click on the New button. An open file dialog will appear, select the file you want to make the relationship by clicking on Open. You will now get a dialog which shows both files and the fields in each. Select a field from each list. If you want to allow creation of related records, click on that box. Click The OK button and your relationship is created.

This is in the manual.

ralphl - Before your response I figured out how to create a relationship the problem I'm having now is totaling the sum for all records lets say field A 10 records. I can total fields within 1 record Sum(Election small::A,Election small::F) Election small is relationship name, but not combined for several records. I think it must be the expression correct.

You must have a relationship between the table you are doing the sum and the table that contains the records you want the sum of, even if they are the same table. The calculation is Sum(TO::Field A). In your relationship chart you have TO1 and TO2 related by some field. Now in the table that TO1 represents make the calculation Sum (TO2:Field A). Replace TO1 & TO2 with the names of the TO's in your chart.