Calling card rules are used for Dial-Up Networking, HyperTerminal, Phone Dialer, and other telephony programs. You can create a custom rule using:

Control Panel / Modems / Dialing Properties / For long distance call, use this calling card / Calling Card / New and follow the dialog box instructions.

The dialing codes you can use are:

0-9: Numbers to be dialed.                                                             ABCD: Characters to be dialed. (Tone dialing only - used for special control on                              some phone systems.)                                                             E: Dial the country code.                                                             F: Dial the area code (city code).                                                             G: Dial the local phone number.                                                             H: Dial the card number.                                                             *,#: Characters to be dialed (tone dialing only).                                                             T: Subsequent numbers are to be tone dialed.                                                             P: Subsequent numbers are to be pulse dialed.                                                             ,: Pause for a fixed time.                                                             !: Flash (1/2 second on-hook, 1/2 second off-hook).                                                             W: Wait for a second dial tone.                                                             @: Wait for quiet answer (ring-back followed by five seconds of silence).                                                             $: Wait for calling card prompt tone.                                                             ?: Suspend dialing until user provides input.
Look at predefined CARD7, MCI long distance via 1-800-674-0700. The LDRule contains 18006740700,,,,,,TH,,FG which means:
                              1. Call 1-800-674-0700.                                                             2. 6 Waits.                                                             3. Dial next numbers as tone.                                                             4. Dial the calling card number.                                                             5. 2 Waits.                                                             6. Dial the area code.                                                             7. Dial the phone number.
The rule is stored in the registry at:

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Telephony\Cards\Card#

where Card# is the entry number. Card0 is (None). Look at Card7 for the Value Names and data types.