calling function from nested master page

[alonso_siang]

i have a nested master page
masterpage.master is the parent master page
and child.master is the child master page from parent master page
i have a new page call new.aspx with child.master as it master page
how do i call the function in parent master page ??
in my child master page i add

<%@ Master Language="VB" MasterPageFile="~/MasterPage.master" AutoEventWireup="true " CodeFile="MAdminMaster.master.vb" Inherits="Teacher_TeacherMaster" %>
<%@ MasterType VirtualPath="~/MasterPage.master" %>

and my new page i add

<%@ Page Title="" Language="VB" MasterPageFile="~/_Maintenance/MAdminMaster.master" AutoEventWireup="true" CodeFile="facility_availability.aspx.vb" Inherits="_Maintenance_facility_availability" %>
<%@ MasterType VirtualPath="~/_Maintenance/MAdminMaster.master" %>

in my master page have a function call
Public Sub DisplayMessage(ByVal strMessage As String, Optional ByVal msgType As Integer = 0)

i not able to call this function in my new page
please help me