When player around block

Hello guys. Maybe someone will help me with this. 
 

So i want to create radiation in my world. I want to implement it like this

I have 1 block and 2 variables. If player around block, one variable will set to 1 if player will go away far enough, to 0

And when the first variable will be 1, the second one will start increasing, if first 0, the second stops increasing at this moment


maybe i can make it easier, idk
also sorry for my english, im french :D