The query would be something like (using a regexp to test for > 100):
$ hledger reg ^exp code:'[1-9]..'
But, hledger register does not show code by default, and does not yet have the --format option (only balance does).
All is not lost however, as code is included in CSV output. So you could get it with
$ hledger reg ^exp code:'[1-9]..' -O csv | SOMETHING
$ hledger reg ^exp code:'[1-9]..' -O csv | dsq -s csv -n -p "select * from {} order by code desc"