アホやからこれくらいしか思いつかないけど

protected override void OnControlAdded( ControlEventArgs e )
{
　e.Control.MouseEnter += new EventHandler( Control_MouseEnter );
　e.Control.MouseLeave += new EventHandler( Control_MouseLeave );
　base.OnControlAdded( e );
}

protected override void OnControlRemoved( ControlEventArgs e )
{
　e.Control.MouseEnter -= Control_MouseEnter;
　e.Control.MouseLeave -= Control_MouseLeave;
　base.OnControlRemoved( e );
}

void Control_MouseEnter( object sender, EventArgs e )
{
　this.OnMouseEnter( e );
}

void Control_MouseLeave( object sender, EventArgs e )
{
　this.OnMouseLeave( e );
}