rlsublime,
Since I don't have long, gonna give you a short answer. This can be accomplished. The way that I personally would accomplish this is to avoid the error completely. I would have the 3 primary key fields on the form unbound, parse the data entered to see if it already exists. If it does load the rest of the data, if it doesn't then create a new record and enable the rest of the fields on the form.

If you need some more assistance on this let me know.

Hope this helps,
Dan