I am trying to calculate the difference between 2 timestamps according to a condition.
All my timestamp Entries are linked to a field named Reference (6 digits number) and I am trying to exclude a part of those Timestamps using this Reference field. What I want to eventually obtain would be ( literally speaking) :
(The minimum Timestamp excluding the one with Reference starting with 'XY') - ( The minimum TimeStamp)
I have tried the following expression but it does not seem to work: