DataGrid Web form button question

Hi

VB,Net / DataGrid / Web form / Bound to Dataset.

I have a Datagrid with a Select Push-button button in column 1. When the
button is pushed no event firers.
Neither of these two events will work UNLESS I switch my button type from
"Push" to "Link"
Private Sub DataGrid1_ItemCommand(ByVal source As System.Object, ByVal e As
System.Web.UI.WebControls.DataGridCommandEventArgs) Handles
DataGrid1.ItemCommand
Dim strtest As String = "test"
End Sub

Private Sub DataGrid1_SelectedIndexChanged(ByVal sender As System.Object,
ByVal e As System.EventArgs) Handles DataGrid1.SelectedIndexChanged
' do something here
End Sub

what am i missing ?

Thanks

Brian