I thought I had a video of how to this but it might have been in the forums at some point. In any case here is an example project I built for the lost video:
FireFromLua.zip (128.0 KB)
I have also attached a much more complicated implementation that I use for Skillz:
FireFromLuaSkillz.zip (3.5 KB)
And finally the Lua portion of the Skillz code:
skillz2.lua.zip (1.1 KB)
Hope this helps to answer your question.