As I mentioned above, there is already a link to that page in there. I found it there by searching the for expression.
I think that Database expressions should get their own little chapter in the help file, where a little of what is possible, and areas of the program where they are permitted (or not, whatever's easier) plus a link to the devzone page can be shown.
You can do so much more with expressions than simply using them to add a filelist column
The formatdate info on the devzone page is out of date:
FormatDate(...): Formats a date value in a specified manner.
Value: the date to format
Formatting: formatting style
Year: 1997
Month: March
Day: 12
Filename: 20040521-032221
Elapsed: 3.2 days ago
Other: flexible formatting (i.e. MMMM-d)
No Date Output: the output when the date is empty (optional: defaults to nothing)
Examples:
FormatDate([Date Imported], elapsed)
FormatDate([Date], MMMM: d, no date)