Adding a column for SUM of timing in CSV or XLS

[conselti]

My need is to add in the export funtions a new column "timing" that contain the sum of time spent to do the work.
Can i do so? How?

I've to calculate the time spent for a list of bugs (filtered by already present filters) and export this information into CSV, XLS, and so on.
It's an apparently simple work BUT i don't understand where i can define a query like "select sum(time_trackung) from mantis_bugnote_table where...." and, after this, how to include this information in the reports.

To do this with mysql it's a very simple work, bu i want to do this with native mantis interface.

Thanks to all for help.