handling nulls in running totals

Its been I while since I’ve been here, but this time I’m back to GET a bit of advice.  I’ve got a situation that I’ve got a resolution for, but I don’t like it, and want to make sure im not missing anything.  Here’s the set up

Crystal 8.5.0.217
Calculating Statistics in a Sub-Report

I’ve got 4 Running totals, 3 of which will be added together to create the denominator of a division stat.  2 of the three will, 9 times out of 10, be Null.  This is because the running total only evaluates on specific criteria (reporting off a 4GL product, evaluation formula is looking for a specific summary account).  As you know, a null value in an aggregate function returns a null value, so I have to either weed out the nulls or set the nulls to zero. My first solution was IF..THEN..ELSE.  But that gets pretty hairy:

IF IsNull({#value 1}) = True AND IsNull({#value 2}) = True THEN
  (IF {#value 3} <> 0 THEN
    {#value 4}/{#value 3}
   )
ELSE IsNull({#value 1}) = True AND IsNull({#value 2}) = False THEN
  (IF ({#value 3}+{#value 2}) <> 0 THEN
    {#value 4}/({#value 3}+{#value 2})
   )
ELSE IsNull({#value 1}) = False AND IsNull({#value 2}) = False THEN
  (IF ({#value 3}+{#value 2}+{#value 1}) <> 0 THEN
    {#value 4}/({#value 3}+{#value 2}+{#value 1})
   )
ELSE IsNull({#value 1}) = False AND IsNull({#value 2}) = True THEN
  (IF ({#value 3}+{#value 1}) <> 0 THEN
    {#value 4}/({#value 3}+{#value 1})
   )

The assumption here is that {#value 3} will never be null. Then in the future, if new values are added to the calculation, the ELSE statements needed to be added will go up exponentially by the number of values in the denominator minus 1.

The other option is to create formulas that check the running total to see if its null, if it is, set it to zero, then use that formula in the calculations.  This way, I don’t have to check for nulls, just that the three columns combined don’t equal 0

I’m sure the easiest option would be to just add all these running totals together into the same running total field, but that cant be done since each value is used else where in the report and must be segregated from the other(Sar-Box compliance).

Which do you feel is the best solution or better yet, what is a more efficient way to do this.  Essentially what I need to do it set the default value of a running total to zero, not just in the report display but in the logic of the report.

Thanks in advance for the help.
mnye