Напишите скрипт. Вызовите это из GNU Parallel:
[... set $START and $COUNT ...]
seq $COUNT | parallel my_script.csh $START {}
my_script.csh:
#!/bin/csh
set START = $1
set i = $2
set REPDATE = "`gdate --date='$START +$i day' +%Y/%m/%d`";
set FILEDATE = "`gdate --date='$START +$i day' +%Y%m%d`";
echo "runf reportname.rep -ps "$REPDATE" -pe "$REPDATE" -o report_"$FILEDATE".csv" \
| reportcli <cli params here>