Auto-adding extension phone number depenting on the ATA extension number

I have several ATAs connect to the same Asterisk Box. Normally, asterisk has to add extension numbers and then configure exactly those number in ATAs with name and password (if applied) in order to make calls. For example, I add extensions from 200-210 for ATA-1, 300-310 for ATA-2, and 400-410 for ATA-3. And of course each ATA has to configure with the extension numbers properly according to its numbers assigned in Asterisk. Now, I would like to do something like this:

  • Each ATA still configure the extension numbers like above but the Asterisk Box does not need to add any extension at all.
  • At any time, the phone from any ATA picks up, the ATA will connect to Asterisk box and the Asterisk auto add the extension number which was assigned in the ATA and continue to process call whatever after that.

Can I do this way?

Any help would greatly appreciated!
Best Regards,