Bomb explode destroy tilemap

So I have this little mini-game where when you set a bomb down it explode using a cheap circle explosion sprite to overlap tilemap to erase the tiles.

Now how do I get it to just to erase a tile range within the explosion radius. I know how to do it from a sprite but id rather do it from a tilemap for easier map making dungeons.

I tried something, look if is that what your are looking for.

https://drive.google.com/file/d/0B5FlDY ... sp=sharing

In my example the bomb(the green sprite) has to be multiple the size of a tile (here a tile is 32x32 the sprite is 64x64). Drag an drop the sprite, then click it to delete the tiles around the sprite.