A few months back a user asked me if there was a way to use VLookup() in a Crystal Report. At the time, I could not think of a way. But recently Millet Software has added this ability to the CUT Light dll. CUT Light adds a number of new functions to your Crystal formula editor and this newest one is called GetXLSOutput() which allows you to tap into calculations stored in a spreadsheet.
In general, this function allows you to capture a report value and use it to fill in a specific cell in a spreadsheet. The function then checks for a value in another call in that spreadsheet and returns it to the report. Obviously, this allows the value that you bring back to be a calculation that depends on the value that you sent to the spreadsheet.
The most common scenario I see for this would be when the spreadsheet has some VLookup tables and logic. The function would allow you to tap into the logic maintained in the spreadsheet. If you come up with a clever use for this, please let me know.
(For examples of my most popular formulas, please visit the FORMULAS page on my website.)