# Open the latest file named something like `report (123).xlsx` in /your/directory/ (OSX)
# Use sort to order the files numerically, starting at the `(` char.
# -t sets the separator
# -g to sort numerically
# -k to choose the column
# Use tail to only select the last result after the sort
# Feed all of the above to the open command as an expansion
open "$(find /your/directory/ -name 'report (*' | sort -t \( -g -k 2 | tail -1)";