alias +dj "+moveup;10waits;-moveup;10waits;+moveup;10waits"
alias -dj "-moveup"
alias 10waits "wait;wait;wait;wait"
Thats the original double jump script that I made. Copy and paste that into your console and bind a key to +dj. If it does not work properly add or delete "wait;"'s in the 10waits alias.
If you need any other scripting help just hollar.