Subscribe to the gridview's RowDataBound event and search for the anchor tag in the item's Controls collection.
    protected void OnRowDataBound(object sender, GridViewRowEventArgs e)
    {
        // this will apply the action in the lambda expression to all controls or sub-controls of the row matching type LinkButton  
        // (you may have a different control type and you may want to alter your lambda expression to check that the control matched is really the control you want to manipulate)
        SearchControls<LinkButton>(e.Row, button => button.OnClientClick = "alert('here');");
    }
    // recursive Control search function
    private void SearchControls<T>(Control start, Action<T> itemMatch)
    {
        foreach (var c in start.Controls.OfType<T>())
            itemMatch(c);
        foreach (var c in start.Controls.OfType<Control>())
            SearchControls<T>(c, itemMatch);
    }