From the NannyMUD documentation

LAST CHANGE

2001-08-12

FUNCTION

NAME
        block_changed_money_hook - 


AVAILABILITY
	/obj/player

DESCRIPTION
	This function is called before money is changed, and if it
	returns non-zero, the change will not take place.

	ARGUMENTS

	block_changed_money_hook(
	  ({ The object giving/taking the money, can be 0,
	     The change,
	     Old money,
	  }),
	  the player
	)


SEE ALSO
        changed_money_hook in hooks/changed_money_hook