Firstly I can't find the syntax for "all cells to the end", all the Help seems to tell me is how to enter a range, i.e. C2:C12 means the range from C2 to C12, but how do you say "to the end"?
In Excel, at least, =SUM(C:C) will sum the contents of numeric values in the whole of column C. Obviously you need to be careful to avoid circular references (i.e. don't put that in column C!), but that should help,
Greg