Yes that is possible, here are the steps:
- On your BB device, create a contact for each person you want to send a PIN message to (if you haven't aready done so)
- In the BB address book, create a new group
- Add every contact you want to send a PIN message to, select PIN when asked
- Save the group
- Now you can send a PIN by chosing "Compose PIN" and then selecting the new group
Remeber that this group is not replicated to your Outlook contacts (or LN or Groupwise)