World: r3wp

The method is pretty simple. Normally the functions return data in 
a particular format. Upon an error though they just return a block 
with 3 elements, the first two of which are lit-words, the last could 
be anything; this is passed directly to apply :cause-error. The error 
block can be recognized and handled easily with this code in the 
REBOL functions that wrap the natives:

 all [block? result lit-word? first result apply :cause-error result]


It's similar to the way error handling is done in the low-level sys 
load functions, particularly sys/load-header. Upon an error, instead 
of a block the function returns a word! value, which can be passed 
to cause-error by the calling function, using code like this:
	set [hdr: code:] load-header/required data
	if word? hdr [cause-error 'syntax hdr source]

Word values are easier to handle safely than error values. Note that 
the argument provided to cause-error in this case is different from 
that provided to load-header: This lets you trigger errors with information 
that load-header isn't provided, giving your errors more context 
that is useful to the programmer. Not exactly the same thing as the 
ODBC driver, but close.