I don't recognize =Roc() as a builtin worksheet function (USA version).
It could be a userdefined function that does a lot of work.
If you hit alt-F11, you get to the VBE (where macros and UDFs live).
hit Ctrl-R to see the project explorer (like windows explorer)
find your workbook/project and double click on it.
If you get prompted for a password, you'll have to go back to the person who
gave you the file.
If you don't get prompted, you can see all the objects that belong to that
project.
(Debra Dalgleish has some pictures (for a different purpose) at:
http://www.contextures.com/xlfaqMac.html#NoMacros
that might be useful to look at.)
You'll want to look under the Modules list and look for something like:
Function Roc(....) as ....
======
And even if you can see the code, you may have to go back to the author to see
what it does.
