[Command Blocks] A snowball that will build for you!

First, make a very fast redstone clock. (Can be made with command blocks. Find the way to do this on youtube by yourself.
Second, connect a command block to the power output.
Third, type in the command right here into the command block:
/execute @e[type=Snowball] ~ ~ ~ /setblock ~ ~2 ~ <block>
Remember to type in the block name or it will not work!
The command will allow you to build without placing any blocks by yourself,
You can also change the block to TNT for fun ;)
Warning: This might mess up your builds if you didn't throw the snowballs properly.

 

I don't think we can have command blocks.

 

You can do this on your own world/server.

 

Command blocks are disabled

I will give it a go