I am trying to set up a template with formulas into which I can simply drop
data into and Excel will then run the calculations. However, the data I will
be entering will have many different lengths. How can I make formulas and
equations to handle the variable lengths of my data?

For example, how do I sum the entries in a column if I do not know how many
entries the column will have? Or, how do I sum a column and omit the #DIV/0
entries that will appear in that column?