What methods are you using to produce the BCC and CC email address entries?
I have a found set... and an email script that collects addresses across found set (the checkmark is selected in the script dialog). The BCC dialog for exaple gets it's records from my contacts' email address.
And what option is used for the TO box? Is it also using the "multiple" option to reference the entire found set of email addresses?
If there is just one address in the TO box, then I can see a way to keep that one address out of the other lists. But if it's also a "multiple/foundset" setting, then I don't see a way to avoid it off hand.
The "To:" address is not using a 'multiple' address. One email using data from the current record. It gets it's address from the contact email address only.
use your script to save the email address of the contact email address in a variable. Then omit the record with this address from your found set using omit record--if this is always the current record in your found set or using constrain found set with the omit option if it is not.
Then refer to the variable in your To box calculation.
Create an email account just for the purpose of these types of emails.
specify the email address to this new account in your TO box. The recipient you used to specify here will still get the email so long as they are listed in either the CC or BCC list of emails.