Function set_block_action:
Defined in module m_blockexits (file: /std/modules/m_blockexits.c)

If given a string, that 'targetted_action' will be done when someone
tries to move a direction we are blocking, unless it starts with a
'#', in which case it is just written to the user.  If it is a function,
then that function will be called with the direction and the person
as args, and the move will be allowed only if the function returns 1.

Prototype:
void set_block_action(mixed ba);
