A telephone dialer includes tables in memory for determining a dialing sequence such as a long distance carrier code to be appended to a dialed telephone number. A variable length prefix portion of the dialed telephone number accesses a prefix table entry that defines an action descriptor for indicating how the telephone number should be processed in a table lookup to determine the dialing sequence. The action descriptor includes a specification of the number of digits to be dialed to trigger a dialing action and may include an indication of an elapsed time to trigger dialing. The action descriptor also includes an indication of the number of digits after the prefix used to determine an action and may specify one of plural ways in which those digits are used to determine the action. The action descriptor also identifies a pointer table to be indexed by the specified digits of the telephone number. The entry in the pointer table points to an entry in the long distance table associated with a particular long distance carrier. The entry in the long distance table then specifies the dialing sequence. The tables may be reprogrammed over telephone lines using DTMF signals or a modem.