MenuDynamicListItem

// The title for the menu item.
string title = "Dynamic list item.";

// The initial selected list item text.
string initialSelectedText = "0";

// Create the callback function for when the left/right arrow
// keys are pressed. Returning a new string value which will become the new
// selected text.
string ChangeCallback(MenuDynamicListItem item, bool left)
{
    // Left will be true when the left arrow key was pressed
    // and false if the right arrow key was pressed.
    if (left)
        return (int.Parse(item.CurrentItem) - 1).ToString();

    return (int.Parse(item.CurrentItem) + 1).ToString();
}

// Use the ChangeCallback function from above to create a new callback delegate.
MenuDynamicListItem.ChangeItemCallback callback = new MenuDynamicListItem.ChangeItemCallback(ChangeCallback);

// optional description
string description = "Description for this dynamic item. Pressing left will make the value smaller, pressing right will make the value bigger.";

// Create the dynamic list item using the variables above.
MenuDynamicListItem dynList = new MenuDynamicListItem(title, initialSelectedText, callback, description);

// Add a menu item to a menu:
menu.AddMenuItem(item);