Kristen,
It sounds like what you really want is a UFL(User Function Library) a UFL is a specific kind of .dll that can be created using VB, C, Delphi, or any other 32 bit programming environment that can create COM components. Once you create a UFL the formulas you define will show up in the Crystal Reports formula editor, just like the built in function. The only catch is that there's no 'formula writer' built into Crystal, you have to be able to program in one of the languages mentioned above. If you want more specific information on this let me know and i will post it.
Ruairi
ruairi@logsoftware.com
Experienced with:
VB6, SQL Server, QBASIC, C(unix), MS Office VBA solutions
ALSO: Machine Control/Automation using GE and Omron PLC's and HMI(human machine interface) for industrial applications