Datagrid and FooterText

I have a footer that I want to use as place to show the balance of each column.

The following does not work FooterText="<%=strBalance%>" (as in nothing shows up in the cell)
Although I can place <%=strBalance%> outside the TemplateColumn attributes and the value shows up correctly.
Is there a way to dynamically change the FooterText or do I need to create
my last row to add the balance value to and forget about doing it in the Footer.

If so how does one create a new DataGrid Row?