Make calculations with customfield and referenced fields

Hi All

I'm new of customfield and also looking for some example i'm not be able to understand how (and if) i can do that.

i need , for enhance with real time variables, to move what is at the moment a fixed computed field calculation in a views custom field.

Now:
I' have a view "content_type_advertising" that has only two referenced field to "content_type_impressions". When i choose "field_site" the view returns "field_total_result" .

This is a computed field "field_total_result" code:

Computed Code:
$node_field[0]['value'] =
$node->field_imps[0]['value']/100 * $node->field_average[0]['value']/1000*$node->field_share[0]['value'];
Display Format:
$display = number_format($node_field_item['value'],2, ',', '.');

What i'm trying to do:
Import in the view all referenced fields except "field_total_result" , add a checkbox with which mark an "attribute" and get views_customfield to make calculation.

Do someone can help me ?
If this is not possible with which way can i solve it?