Prime magnitude and keys...a ?

[SINCLAIR DOUGLAS N]

> I was wondering if anyone is aware of a function or test which would allow
> a person to feed PGP or other RSA algorithm a test key and then look at
> the result and determine if the key was greater or lesser than the 
> actual key? 

I hope not.  If such a thing existed (if I understand your description
correctly) RSA could be cracked by a binary search of keyspace.  The
search would be O(log(n)), meaning it would be directly linear with
the number of bits in the key.