• Login to the system administration
• Navigate to 'DIDs'
• Click on the 'Add DID' button
• Click on 'Advanced Options'
• Select one of the existing trunks under the 'Trunk' field
• Enter the starting value into the 'DID/Channel (start)' field (e.g. 55510205)
  
• Set the 'Range' value to 'Yes'
• Enter the end value into the 'DID/Channel (end)' field (e.g. 55510215)
• Set 'Destination'='Extension'
  
• Set 'Value'='1000'
  
• Click on 'Save'

All calls made through the selected trunk to numbers from 55510205-55510215 will point to the same destination, Extension '1000'.