Yes, you can manually add a list of telephone numbers to the Blacklist memory of your Blocker. 

There are 3 ways of adding numbers to the BLACKLIST.
1) Wait for the unwanted call to ring, and press the "BLACKLIST" button (Recommended)
2) Follow step 5.0 in the 
manual at http://hqtelecom.com/TLock-Pro-CallBlocker-N2-UserManual.pdf
3) To add these numbers to the blacklist, follow these steps:

a) Connect a telephone to the PHONE port for your Blocker.

b) Dial a number you want to block using the dial-pad of the telephone connected to the PHONE port (you can hang up).

c) Now, press OUT button to view the outbound calls.  Then use the scrolling Left/Right buttons to find the number you just dialed.  Press the “Blacklist” button to add it to the backlist memory. Repeat these steps for each number you want to block.