triggering an event in another C# script

hi, this has probably been asked a million times however i cant seem to get it to work.

I have two scripts. one event occurs in script A and should trigger another in Script B.

 if(transform.position.y < 0)
     //trigger in other script B

And then in my other script, B i want something like this:

 //if Event happened in script A
     blockcount--;

I've looked everywhere for an answer but nothing works, can someone help? would be much appreciated!