Try using L2.NET bot. With it you can use commands like /sleep, /sit, /assist.
You could for example make a macro for that character:
/invite Playername
Then in the leveling script you use (get one from the site and modify as needed) the hotbar button you put the macro to.
When you want to leave then:
COMMAND "/leave"
I can't really explain very precisely. It's not like l2walker, you have to use scripts to level up.