ComboBoxes in DataGridView

[woogoo]

I'm having problems implmenting ComboBoxes within a DataGridView. I have a grid containing 3 columns, each of these columns is defined as a DataGridViewComboBoxColumn.

At form load I want to populate the column on row 0 col 0 with a TimeInterval class. From here the user selects a time e.g. 07:00 then moves to col 1, row 0. At this point I now need get the selected index from col 0, row 0 so I can use it to exclude TimeIntervals all time intervals before this period prior to adding them into the row 0, col 1 combobox.

I've tired various approaches to this but when using my TimeInterval Class the datagrid complains that the data is invalid.

Public Class TimeInterval
    Private m_ID As Integer
    Private m_Interval As String

    Public Sub New(ByVal ID As Integer, ByVal Time As String)
        m_ID = ID
        m_Interval = Time
    End Sub

    Public ReadOnly Property ID() As Integer
        Get
            Return m_ID
        End Get
    End Property

    Public ReadOnly Property Interval() As String
        Get
            Return m_Interval
        End Get
    End Property

    Public Overrides Function ToString() As String
        Return m_Interval
    End Function
End Class

The above class contains an ID and a Time in the format of 00:00, and a range of these exists in a TimeIntervalsCollection.

Can anyone help me out here or point me in the direction of a good resource ComboBox use in DataGridViews.