I know you got yours working, but in order to keep from using another sprite detector, you could do:
For Each Sprite(or family enemy ect...)
->Distance(you.x, you.y, Sprite.x, Sprite.Y)<100
-->Spawn whatever. Do whatever.
->Distance(you.x, you.y, Sprite.x, Sprite.Y)>=100
-->Destroy whatever. Do whatever Else
I dont know if it would make anything better or worse...