Building a weekend report

[DAGgernaut]

I am trying to build a weekend report which includes opening multiple files for each session of the race weekend (P1, P2, Q, R1, R2) as an example. What I would like is to produce is a total of all of the opened Outings:Sessions. For example total distance over the race weekend. I can easily get the totals for any one session but I cant figure out how to get the grand total for all open sessions. integrate across multiple files for a single value result.

I think I may need to use range_change("Outings:Sessions") in a stat_max but I haven't been successful. Any help would be appreciated.