>
>Do you have samples or ideas how this should be done?
>

Just expose it as an event on the user control, then call that event from within the user control, ex.

In your user control:

- Create a new event that mimicks the current SelectedIndexChanged event of the control
- Create a OnSelectedIndexChanged method which will raise the event
- Hook up the SelectedIndexChanged handler like you normally would and have it call the OnSelectedIndexChanged method.

In your page which uses this user control:

- Hook up the event to your new SelectedIndexChange event on the user control.

// User Control
public event EventHandler SelectedIndexChanged;

public virtual void OnSelectedIndexChanged(object sender, EventArgs e)
{
    if (this.SelectedIndexChanged != null)
        this.SelectedIndexChanged(sender, e);
}

protected void cboList_SelectedIndexChanged(object sender, EventArgs e)
{
    this.OnSelectedIndexChanged(sender, e);
}