Sum on list : sum on every numeric field

Hello,

sum on list is a usefull option but, sometimes, it will be great to be able to summarise every numeric fields.
For exemple, in project expense, beeing able to get sum of planned an real amount, and, more, with personalised field.

So, it could be done with adding a line into list (great if this line is top of the table, last line if more convenience to build - not need to compute values before building the table) with sum of every field type int or decimal). This line could be displayed with gray shade to highlight it.
 

Regards,