Functions not documented?

if you look at Chris Hays's Blog
http://blogs.msdn.com/chrishays/archive/2004/07/23/193292.aspx

we find functions which were not documented in Reporting Services.
eg.
=Ceiling(RowNumber(Nothing)/3)

now where do i go to find more goodies like that? microsoft has given us alot of good features with reporting services. if only we know how to use them...
All of the aggregate functions are documented in the included docs (http://msdn2.microsoft.com/en-us/library/ms159269(en-US,SQL.90).aspx). Other functions are part of the .NET Framework. The new Expression Dialog has a list of commonly used functions (see also http://msdn2.microsoft.com/en-us/library/ms157328(en-US,SQL.90).aspx).