Hi Rob,

     Sorry, but our WebGrid does not support that feature. However, we can use ColumnAction, so, there is a context menu if you click on the column header and create a new menu item to it and works as a new function to it for the workaround. 

     First, we need to show the column action in the WebGrid by:

        <LayoutSettings ShowColumnAction="True">

     Then, using the OnColumnContextMenu client action, we can create a new item and call a new function. Here is the snippet:

        function WebGrid1_OnColumnContextMenu(controlId, col, menu, isGroup, location)
        {
            var WebGrid1 = ISGetObject(controlId);
            
            var separator = new WebMenuItem();
            separator.Type = "Separator";
            separator.Name = "MySeparator";

            var menuItem = new WebMenuItem();
            menuItem.Text = "New Function";
            menuItem.Name = "MyMenu";
            menuItem.OnClick = "newFunction";

            menu.Items.Add(separator);
            menu.Items.Add(menuItem);
            return true;
        }

        function newFunction()
        {
            alert("This is a new function");
        }

      I hope it helps. Thank you and have a nice day.

Best Regards,

Andi Santoso