Establishing a Dial up Connection after it is disconnected

I am using a dial up connection for net connectivity. The net connectivity is established using a GSM GPRS USB Modem connected to a PC Com Port. I am using rasdial command to connect to Internet. Once connected, I am pinging my server periodically to check and ensure that net connectivity is in place. When Ping test fails (this happens irregularly after 2 hrs, 3 hrs or sometimes after 5 hrs also), I try to disconnect the established connection using rasdial disconnect command - however this is not successful every time a ping fails for reasons not known to me. (somewhere I read that rasdial disconnect command will not work after disconnection). Given the above scenario, i am not able to reconnect or reestablish the net connectivity unless and until I restart the PC and this is not a possible option as my application is running and this will not allow PC restart. Want your recommendations /advise as to how to reconnect to a dial up connection after it is disconnected ? What are the possible ways and means for this . Regards