If you mean all the BB users in your address book then what you can do is create an group in your address book and add all your BB users' PINs to the group. Then, when composing a PIN message, you can choose that group as the recipient.
To make a group you go to the Address Book, press the BlackBerry menu key, then select New Group. You can then add your contacts that way. If your contacts already have the PIN programmed in the contact information (which is an available field on devices with 4.3 and higher, I believe), then when you add that person to the group it will prompt which address (e-mail, phone number or PIN) you want to use.