Hi, I have a question!

I'm making a custom wand for my server and want to add a blaze effect. I already made 2 working spells, a spells selector and added perms and an on-death event. However, I can't seem to find a way to put fire on top of blocks in a certain radius. when using a simple radius and setting the blocks within that radius it destroys all blocks within the radius. (completely logical)

Code (Text):

1. on left click:
2.     if name of player's tool is "&4&lDarkWand":
3.         if {spell} is 3:
4.             loop blocks in radius 4 around player:
5.                 set loop-blocks to fire

Is there a way to use a radius from the player and putting fire on top of the blocks, not destroying any?

Any response would be greatly appreciated!