I think it works like native ASP.NET controls:
RadControls for ASP.NET AJAX Documentation - Event sequence
<radG:RadGrid runat="server" ID="rgUsers" OnItemDataBound="rgUsers_ItemDataBound">
protected void rgUsers_ItemDataBound(object sender, GridItemEventArgs e)
{
if (e.Item.ItemType == GridItemType.EditItem)
{
User user = (User)e.Item.GridDataItem;
UserEditor userEditor = (UserEditor )e.Item.FindControl("UserEditor");
UserEditor.User = user;
}
}