asp:Bound Column format question

How can I assign a CSS class to the last row of data in asp:BoundColumns? Please see the attached code snippet. I would like to have the last row of data to be bold.

<Columns>
<asp:BoundColumn ItemStyle-Width="100" HeaderText="Date Worked" DataField="StartDate">
<HeaderStyle CssClass="InvoiceHead"></HeaderStyle>
<ItemStyle CssClass="InvoiceItems"></ItemStyle>
</asp:BoundColumn>
 
<asp:BoundColumn ItemStyle-Width="150" HeaderText="Employee Name" ReadOnly="true" DataField="EmpName">
<HeaderStyle CssClass="InvoiceHead"></HeaderStyle>
<ItemStyle CssClass="InvoiceItems"></ItemStyle>
</asp:BoundColumn>

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