How can i make a variable that is linked to a block?

So I have this teleporter block that links to other teleporters through this tablet the way it works is it when sneaking and right clicking a teleporter with it in your hand it links the tablet to that location and when right clicking another teleporter it just says that it's a teleporter as a placeholder because I don't know how to get the location from the variable and put it into a separate variable for the block only