Call public function from another function using VB.Net in ASP.Net

Hello,

I have this public function, but I just want to call it from the login page when it’s click. Can you show me how I can do that please?

This is the public function.

    Public Function AuthenticateEmployee(ByVal Username As String, ByVal Password As String) As Boolean
        Try
            Dim Entry As System.DirectoryServices.DirectoryEntry = New System.DirectoryServices.DirectoryEntry("LDAP://csufacad.fullerton.edu", Username, Password)
            Dim nativeObject As Object = Entry.NativeObject 'Authenticate username and password
            Return True 'Correct credentials
        Catch
            Return False 'Incorrect credentials
        End Try
    End Function

This is the login page. 

    Protected Sub Login1_LoggedIn(sender As Object, e As System.EventArgs) Handles Login1.LoggedIn

        Dim connString As String = ConfigurationManager.ConnectionStrings("DBHUSRConnectionString").ConnectionString
        Dim DBConnection As SqlConnection = New SqlConnection(connString)
        Dim DBCommand As SqlCommand
        Dim DBReader As SqlDataReader
        Dim thisUserName As String

        If DropDownList1.SelectedValue = "AD" Then

            DBConnection.Open()
            DBCommand = New SqlCommand("QGlobalUserRecords_sp", DBConnection)

            DBCommand.CommandType = CommandType.StoredProcedure
            DBCommand.Parameters.AddWithValue("@UserID", Login1.UserName())
            DBReader = DBCommand.ExecuteReader()


            While DBReader.Read()
                If Login1.UserName = DBReader("WM_UserName") Then
                    thisUserName = DBReader("WM_Comments")
                    Select Case thisUserName
                        Case "Agency"
                            Response.Redirect("~/Agency/Agency.aspx")
                        Case "Admins"
                            Response.Redirect("~/Admin/Default.aspx")
                        Case "STUHUSR"
                            Response.Redirect("~/Advising/StudentRecord.aspx")
                        Case "Faculty"
                            Response.Redirect("~/Faculty/Faculty.aspx")
                    End Select
                End If
            End While
        End If

        If DropDownList1.SelectedValue = "ACAD" Then
            Response.Redirect("~/Student/StudentAssignment.aspx")
        End If
        DBConnection.Close()

    End Sub

thanks