Hi,
yes this is possible, but you need to create a simple plugin, follow this example:
- Download, Install and Enable Skeleton Plugin (you will find it at http://docs.easy-profile.com/index.php/article/triggers)
- Open file /plugins/jsn/skeleton/skeleton.php
- remove samples functions: triggerFieldAvatarUpdate, triggerProfileUpdate
- add function like this:

public function triggerProfileUpdate($user,&$data,$changed,$isNew){ 

    // SUM

    $data['field1'] = $data['field2'] + $data['field3'];

    // CONCAT

    $data['field1'] = $data['field2'] . $data['field3'];

    // SUM FROM CHECKBOX OPTIONS, 

    // The checkbox can have multiple values (2 or more options), so the value is stored in JSON format

    $values = (array) json_decode($data['field2']);

    foreach($values as $value){

        $data['field1'] += $value; // sum of options value

    }

}

with this way you can do operations between fields, you need only to write your operation
docs about our triggers at http://docs.easy-profile.com/index.php/article/triggers

NOTE: This code is not tested and not supported, this is only for example purpose. You need to have a minimum of PHP knowledges

Thanks. Can the fields be text with a format set to integer or do they have to be of type number?
The fields I want to add are text integer but the code you gave me is apparently returning nothing in the resulting field?

OK. I found that if the field is having a decimal, the sum is not done. Plus I don't know why but my integer fields accept only , for the decimal instead of the . Maybe that's the reason why the sum is not working when there is a number with a , ?

Hi,
we recommend to use text field type, it is more flexible.
To restrict numeric values you can set "format allowed" option to "decimal" like screenshot.

in php the decimal separator is ".", so you need to convert all "," occurrences before the sum.

Thanks for your answer. My fields are defined now as Text and option decimal. But when using a "." I got an "error" message with the field highlighted in red. Only with a "," I can submit the new value without error. How can I change that so my users can use "." instead of ","?
Thanks.