Frequency change

Our cable system has again moved frequencies around (I work for Comcast). I have about 1000 of the RCA modems that were out in the field six months ago, before we changed the frequencies. Now, we are trying to use these modems again. In some areas we have a 597 mhz and in others 567... there are also a few with a dual downstream (both 567 and 597). The problem I am having is, if there is a dual downstream, the modem will only go as far as 597, thinking that that is the DS it is supposed to lock on. Is there any way to manually tell the modem which frequency to lock on? If not, I am stuck with 1000 useless modems in inventory. The terayon modems have a specific web page where you can actually tell the modem which frequency to lock on... This is what I am looking for, Please Help!!!! I have done the manual resets (with the pen on the back of the modem), and the power cycles (pulling the power plug) to no avail...