I am new to asp.net and I'm trying to build my first web page, but when I try to fill a dataset at the page load event I get an error:

object reference not set to instance of object.

Am I missing something? I've done this many times in vb.net. I can't figure out how to step through my code like I do when I'm creating a desktop app, so I don't know exactly where it's failing. I like to be able to see the values of things as it goes through the code.

Code:
 Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        Label2.Visible = False

        Dim dsCheckExisting As New System.Data.DataSet()
        dsCheckExisting.Clear()
        Dim adLookup As New OleDb.OleDbDataAdapter
        adLookup.SelectCommand = New OleDb.OleDbCommand
        Dim cnxAd As New OleDb.OleDbConnection
        cnxAd.ConnectionString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" & Chr(34) & "C:\xxx\db1.mdb" & Chr(34) & ""
        Dim joe As String = "OCYNFC005679699.994/21/20125/5/2012"

        With adLookup.SelectCommand
            .Connection = cnxAd
            .CommandText = "select * from sheet1 where [unique]=" & joe & ""
            .CommandType = CommandType.Text

        End With
        Try
            cnxAd.Open()
            adLookup.Fill(dsCheckExisting, "sheet1")
            cnxAd.Close()
        Catch ex As Exception
            cnxAd.Close()

        End Try
        Dim dr As DataRow
        If dsCheckExisting.Tables("sheet1").Rows.Count > 0 Then
            For Each dr In dsCheckExisting.Tables("sheet1").Rows
                Label1.Text = dr("booked")
            Next
        End If
       
    End Sub