ASP.NET: CheckBoxList specify number of columns

How do I specify that I want two columns on a checkboxlist? Below is my code:

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
    If Not Page.IsPostBack Then
        Dim di As New IO.DirectoryInfo("\\bk00app0001\Images\")
        Dim imageArray As IO.FileInfo() = di.GetFiles()
        Dim image As IO.FileInfo

        'list the names of all images in the specified directory

        For Each image In imageArray
            CheckBoxList1.Items.Add(image.Name)
        Next
    End If
End Sub

Protected Sub btnDelete_Click(ByVal sender As Object, ByVal e As EventArgs) Handles btnDelete.Click

    For count As Integer = 0 To CheckBoxList1.Items.Count - 1
        If CheckBoxList1.Items(count).Selected Then
            File.Delete("\\bk00app0001\Images\" & CheckBoxList1.Items(count).ToString)
            CheckBoxList1.Items.Remove(count)
        End If
    Next

    Response.Redirect("Delete.aspx")

End Sub