1. Set up however many armor stands you need random options. Name them all the name name using name tags (for example: "target").
2. Run this command:
/execute @r[type=armor_stand,name=[COLOR=#b30000]target[/COLOR]] ~ ~ ~ setblock ~1 ~ ~ redstone_block
(you can change the coordinates and name to what you need)
This will place a redstone block next to one of the armor stands randomly, and each of these blocks could be further be hooked up to more commands, a redstone circuit, etc.
View reply.