that i do not know...
but i think you could do it this way, but i have not tried it...
import the information into a new record, but also import the company and contact details of the original record you need this to go in...
Then you could do a merge and purge which then should combine both the records together and joining the notes fields without clearing any information...
But you may also be able to use goldbox/inaport for this, but again i have not used goldbox, i've only heard of function that is can do
Sorry you have got me thing, if you cross reference your information against goldmine to get the accountno of the records, then we you are importing the information you can match the accountno against goldmine, and this may just import the notes, and not erase any previous information, that worth a try... just use a backup database...
If you unsure about anything which i have said then please let me know as i can explain it in more depth for you.
Hope this all helps....