Adding "code" to SSRS Reports, I finally get it....
I finally figured out how and when to use the code portion of SSRS reports. Basically, we need to write code when there is not a default function available that serves our needs. In this instance, I created code named Divider. There is not a default SSRS function to determine if the divisor is a zero in SSRS. This code creates a function that allows us to pass two values to the code, and if the denominator is a zero, it returns zero.
If you try do do this as a regular math expression, SSRS will throw an error in your report. You can also create a complicated iff statement, but this is much more efficient, if you can understand how it works. This is the first instance I've found of using the code section in SSRS.