Question Allowing Staff to promote guests

Hi,

Im currently using PEX for my server. I want it so that Staff rank can only promote players of 'Guest' rank to 'Member' rank, but no higher and i dont want them to able to demote. For the record, Member rank is one higher (so lower number) on the ranking system to Guest (Staff is a few levels down the rank ladder at level 600). I've managed to do this before on a server i did a while back i know its just a few PEX nodes i need to add to Staff ranks permissions and the ranking ladders which i have setup. Just need someone to jog my memory. I would preferable like it so that Staff can just type '/pex promote {player}' and it would promote a Guest user to Member but no higher and cant demote either. Please help thanks:

groups:
New:
permissions:
- modifyworld.*
- essentials.kit
- essentials.kits.starter
- essentials.balance
- essentials.balancetop
- essentials.balance.others
- essentials.pay
- essentials.help
- essentials.ignore
- essentials.list
- essentials.mail
- essentials.mail.send
- essentials.motd
- essentials.msg
- essentials.rules
- essentials.ping
- essentials.delhome
- essentials.home
- essentials.sethome
- essentials.tpaccept
- essentials.tpdeny
- essentials.suicide
- essentials.spawn
- essentials.signs.use.disposal
- essentials.signs.use.balance
- essentials.chat.url
options:
build: true
rank: 1100
prefix: '&e[New]&f'
default: true
Member:
permissions:
- essentials.warp.list
- essentials.warp
- essentials.signs.use.warp
inheritance:
- new
options:
build: true
rank: 1000
prefix: '&a[Member]&f'
default: false