check if chunk is loaded

I'm making some "remote control" item for a mod that can trigger a block from a distance. it works fine, but there is an issue.

it's supposed to display a message if the block is unreachable (in unloaded chunk) or doesn't exist.

when the block doesn't exist, it works fine. but i cannot find a way to detect if the block is in an unloaded chunk.

is there a procedure that allows it or do i have to use distance?