vgroup_id	IN:	Vgroup identifier returned by Vattach
	obj_ref	IN:	Reference number of the object

	Purpose	Determines whether a data object is a vdata within a vgroup.
	Return value	Returns TRUE (or 1) if the object is a vdata and FALSE (or 0) otherwise.
	Description	Visvs determines if the object specified by the reference number, obj_ref, is a vdata within the vgroup identified by the parameter vgroup_id.

	FORTRAN	integer function vfisvs(vgroup_id, obj_ref)
		integer vgroup_id, obj_ref