Would this be similar to counting vote totals in the polls?
An OnExternalDataBound property?

Thanks,
Richard

Hello,

You can use slightly modified approach as it is described in one KB article here: http://devnet.kentico.com/Knowledge-Base/Web-parts---Controls/How-to-display-number-of-records-in-repeater.aspx

Basically you just need to count items in repeater used within Message Board control: ~\CMSModules\MessageBoards\Controls\MessageBoard.ascx.cs

Please add following code to the ReloadBoardMessages() method just after repeater's data bind call like this:

this.rptBoardMessages.DataBinding += new EventHandler(rptBoardMessages_DataBinding);

And create new method like this:

    void rptBoardMessages_DataBinding(object sender, EventArgs e)
    {
        if (!CMS.GlobalHelper.DataHelper.DataSourceIsEmpty(rptBoardMessages.DataSource))
        {
            System.Data.DataSet dv = rptBoardMessages.DataSource as System.Data.DataSet;
            if (dv != null)
            {
                ltlRepeaterCount.Text = dv.Tables[0].Rows.Count.ToString();
            }
        }
    }

Then you can just add label control to the HTML code to show up the number:

<asp:Label ID="ltlRepeaterCount" runat="server" ></asp:Label>

Best Regards
Ondrej Vasil

For anyone who will look for same question but for Kentico 6 - you can use following macro:
{%CurrentDocument.MessageBoards.MessageBoard.Children.BoardMessages.Count%}