The TAPICLIENT_LineGenerateDigits function is called during a call to the lineGenerateDigits function.
LONG TAPICLIENT_LineGenerateDigits(
HMANAGEMENTCLIENT hmClient,
LPTAPIPERMANENTID lpPermanentID,
DWORD dwReserved,
LPWCSTR lpszDigits
);
lineGenerateDigits, TAPICLIENT_ClientInitialize, TAPIPERMANENTID