How to make a Creeper spawning blocks at explosion

Hi,

I'm trying to add Creepers to my mod, but I can't figure out, how to place or fill a certain block when the creeper explodes.
The "When entity dies" procedure doesn't work when he explodes, it only works when the creeper dies "properly" (Killed by Player, fall damage,...)
I also don't know how to use the AI / custom tasks builder in MCreator. There's no template for Creeper just for normal aggressive mobs. So I'm using Creeper A.I.
Is there any way to make this working? Even if it's without Creeper A.I. selected (but i need help creating a custom A.I. then)

Thank you!