h_id	IN:	Access identifier returned by Hstartread or previous Hnextread
	tag	IN:	Tag to search for
	ref	IN:	Reference number to search for
	origin	IN:	Position to begin search: DF_START or DF_CURRENT

	Purpose	Searches for the next data descriptor that matches the specified tag and reference number.
	Return value	Returns SUCCEED (or 0) if successful and FAIL (or -1) otherwise.
	Description	Wildcards apply. If origin is DF_START, the search will start at the beginning of the data descriptor list. If origin is DF_CURRENT, the search will begin at the current position. Searching backwards from the end of a data descriptor list is not yet implemented.
		If the search is successful, the access identifier reflects the new data element, otherwise it is not modified.