Block:

block: < call>[,< call>]...

VariableComment
call source call from which no frames are accepted

Wildcards may be used to match the incoming callsigns.

*   Matches any 0 or more character(s).
?   Matches any 1 character.
@  Matches any alpha character.
!    Matches any digit.

More info see: Wildcards.

example:

block: N0CALL,NOCALL,MYCALL