If it is one or two specific numbers, it MIGHT be possible using ARS, but you will need a good understanding of how ARS works. When the original number is dialed, it matched a pattern in the route group. Then proceeds to the facility group, the dial rules do not echo any of the number, but does ADD the new number. Again, It will take someone with a good understanding of ARS and will require proper testing. If it is not tested properly it could affect other outbound calls.