This might get you started:
<font face=Calibri><SPAN style="color:#00007F">Sub</SPAN> foo()<br> <SPAN style="color:#00007F">Dim</SPAN> i <SPAN style="color:#00007F">As</SPAN> <SPAN style="color:#00007F">Long</SPAN><br> <br> i = Cells(Rows.Count, "C").End(xlUp).Row<br> <br> Cells(i + 1, "C").Value = Application.WorksheetFunction.Sum(Range("C1:C" & i))<br> <br><SPAN style="color:#00007F">End</SPAN> <SPAN style="color:#00007F">Sub</SPAN></FONT>
HTH,