Page Load not firing?

Firstly I should say that this isn't my code so bare with me.....
I d/l it from here if you need to see the original (zip file at foot of page)
http://aspnet.4guysfromrolla.com/articles/041603-1.2.aspx

I split the code and put the vb into the code behind file.
It has this sub...
Public Sub Page_Load()
        tempDate = Me.Calendar1.TodaysDate
        If Not (Page.IsPostBack) Then
            Get_DBItems()
        End If
    End Sub

and in Get_DBItems it errors on this line....
parameterDate.Value = tempDate.AddDays(-40) saying the result is not a date.
When I check the initial value of parameterDate.Value is "nothing"
Strange thing is that I put a breakpoint in the Page_Load sub and it never seems to get there, when I launch from VS2005 and goes straight to the breakpoint within Get_DBItems.

I'll post my aspx and aspx.vb below.. any ideas?
The aspx is inside a <asp:content>

<div id="daydetail" runat="server" visible="false">
<h2>Details for <span id="selectedday" runat="server" /></h2>

      <span id="daydetail_render" runat="server" />
</div>      

<div runat="server">
   <asp:Calendar id="Calendar1" OnDayRender="Calendar1_DayRender"
               OnSelectionChanged="Calendar1_SelectionChanged"
            OnVisibleMonthChanged="MonthChanged"
               DayStyle-Height="100" DayStyle-Width="75" DayStyle-HorizontalAlign="Left"
            DayStyle-verticalalign="Top"
            NextPrevFormat="FullMonth" SelectionMode="Day"
            TitleStyle-Font-Bold="False"
            TitleStyle-Font-Size="12" BackColor="white" BorderColor="#000000"
            CellPadding="2" CellSpacing="2" Runat="server"
            SelectedDayStyle-BackColor="#faebd7"
            SelectedDayStyle-ForeColor="#000000"
            OtherMonthDayStyle-ForeColor="#C0C0C0" DayStyle-BorderStyle="Solid"
            DayStyle-BorderWidth="1" TodayDayStyle-ForeColor="Black" Height="600"
            Width="750">
      </asp:Calendar><br><br>
      
</div>

then the code behind.....

Imports System.Data
Imports System.Data.SqlClient

Partial Class HR_Calendar_Default
    Inherits System.Web.UI.Page
    Public Structure MyDates
        Dim _Title As String
        Dim _Date As DateTime
    End Structure

    Public MyCollection As Collection
    Public tempDate As DateTime

    Public Sub Page_Load()
        tempDate = Me.Calendar1.TodaysDate
        If Not (Page.IsPostBack) Then
            Get_DBItems()
        End If
    End Sub

    Public Sub Get_DBItems()

        Dim myCommand As SqlCommand
        Dim ConnectionString As String = System.Configuration.ConfigurationManager.ConnectionStrings("IntranetConnectionString").ConnectionString
        Dim myConnection As System.Data.SqlClient.SqlConnection = New System.Data.SqlClient.SqlConnection(ConnectionString)

        myCommand = New SqlCommand("GetHRCalendarItems", myConnection)
        myCommand.CommandType = CommandType.StoredProcedure

        '// Set to 40 days before the current value of tempDate
        Dim parameterDate As New SqlParameter("@_Date", SqlDbType.DateTime)
        parameterDate.Value = tempDate.AddDays(-40)
        myCommand.Parameters.Add(parameterDate)

        '// Set to 40 days after the current value of tempDate
        Dim parameterDate2 As New SqlParameter("@_Date_Plus_1", SqlDbType.DateTime)
        parameterDate2.Value = tempDate.AddDays(40)
        myCommand.Parameters.Add(parameterDate2)

        Dim myDataReader As SqlDataReader
        myConnection.Open()
        myDataReader = myCommand.ExecuteReader()

        Dim temp As MyDates
        MyCollection = New Collection()

        While (myDataReader.Read())
            '//Created each time through the loop to get a new item to load and add to the collection
            temp = New MyDates()

            temp._Title = myDataReader.Item("Title")
            temp._Date = CDate(myDataReader.Item("_Date"))

            MyCollection.Add(temp)


        End While

        '// Close
        myDataReader.Close()
        myConnection.Close()



    End Sub


    Public Sub Calendar1_DayRender(ByVal sender As Object, ByVal e As DayRenderEventArgs)
        Dim Item As MyDates  '//Temporary storage for looping through the collection
        Dim DayHold As DateTime = "01/01/1900" '//Temporary date to check for multiple items per day
        Dim MultipleItemDay As Boolean = False

        '// Set to true if the date is in the collection and needs to be displayed
        Dim DayTextHasChanged As Boolean = False

        '//To build the string for the contents of the table cell
        '//I'll use the stingbuilder class instead of concatenation
        Dim temp As StringBuilder

        If IsNothing(MyCollection) = True Then
            Get_DBItems()
        End If

        For Each Item In MyCollection
            '//The collection is loaded in date order.  So, if the date is different than the DayHold variable
            '//And I've already found the right day in the collection, I can exit the for loop
            If DayHold <> Item._Date Then
                If DayTextHasChanged = True Then
                    Exit For
                End If
                MultipleItemDay = False
                DayHold = Item._Date
            Else
                MultipleItemDay = True
            End If

            '//If I've found a date matching the current date...I need to create the appropriate text
            If e.Day.Date = Item._Date.ToString("d") Then
                If MultipleItemDay = False Then
                    temp = New StringBuilder() '//Create a new stringbuilder object
                Else
                    temp.Append("<br>") '//add a seperator to the stringbuilder
                End If
                temp.Append(Item._Title.ToString())
                temp.Append("</span>")
                DayTextHasChanged = True '//Set the flag
            End If
        Next

        '//If there was an Item for this day, add the stringbuilder text to the table cell
        If DayTextHasChanged = True Then
            e.Cell.Controls.Add(New LiteralControl(temp.ToString()))
        End If

    End Sub

    Public Sub Calendar1_SelectionChanged(ByVal sender As Object, ByVal e As EventArgs)
        Dim ConnectionString As String = System.Configuration.ConfigurationManager.ConnectionStrings("IntranetConnectionString").ConnectionString
        Dim myConnection As System.Data.SqlClient.SqlConnection = New System.Data.SqlClient.SqlConnection(ConnectionString)
        Dim myCommand As SqlCommand
        Dim myDataReader As SqlDataReader
        myCommand = New SqlCommand("GetHRCalendarSingleItem", myConnection)
        myCommand.CommandType = CommandType.StoredProcedure

        Dim parameter_Date As New SqlParameter("@_Date", SqlDbType.DateTime, 8)
        parameter_Date.Value = Calendar1.SelectedDate
        myCommand.Parameters.Add(parameter_Date)

        myConnection.Open()
        myDataReader = myCommand.ExecuteReader()

        Dim temp As String = ""
        Dim Category As String = ""

        While (myDataReader.Read())
            temp &= "Title : <a href=""edit.aspx?ID=" & myDataReader.Item("ID") & """>" & myDataReader.Item("Title") & "</a><br>Date : " & myDataReader.Item("_Date") & "<br><br>"
        End While
        daydetail.Visible = True
        daydetail_render.InnerHTML = temp
        myDataReader.Close()
        myConnection.Close()
        selectedday.InnerHTML = Calendar1.SelectedDate.ToString("d MMM, yyyy")
        tempDate = Calendar1.SelectedDate '//
        Get_DBItems()
    End Sub

    Public Sub MonthChanged(ByVal source As Object, ByVal e As MonthChangedEventArgs)
        '//Set the tempDatevariable to the value in the MonthChangedEventArgs NewDate property
        tempDate = e.NewDate

        '//Reload the collection
        Get_DBItems()
    End Sub

End Class