Adding AT commands to a dial up configuration

I have a bit of a problem! We have about 355 mobile computers running Windows CE.NET 4.20 across 3 states. Recently the connections to the Verizon data network have not been very stable particulary in the Atlanta, GA and Ft. Lauderdale, FL areas. I called Verizon to see if there were any data network problems in these areas (of course there are non). I asked the Verizon rep if the modems were maybe having a problem with roaming. As it turns out this is the case and the problem is easily addressable by using an AT command via Hyperterminal. However, these computers are locked down in the field and I need an easy way to make sure the modems dial *22899 each time they connect to update the PRL (Preferred Roaming List). Can this be added somehow into the network configuration setting? We are using CDMA modems. Not sure if this is enough info.