I don't see anything on Chip's page about error number.
On further consideration and correspondence with Russell from bettersolutions.com (same as your link), i believe the range for custom errors is -2147221504 to -1.
Adding vbObjectError to my custom number will push my custom number down to around -2 billion.
If my custom numbering starts counting from there, and if VB reserves 0 to 513, then the top of the custom range must be -1.
If all that is true, then the following just confuses me again:
Plus, as mentioned, bettersolutions Codes page shows native errors of 520, 521, some 700's, and some 31000's."The range 513 - 65535 is available for user defined errors"
Also, if i'm correct, then this isn't exactly correct (from bettersolutions):
In fact, custom numbers should be less than 0."For any user defined errors, these should be greater than vbObjectError"
Another wrench in the works: If i'm supposed to add vbObjectError, and if 513-65535 is usable, then why does `Err.Raise vbObjectError+515` give me a native error!?