This accompanies my Caller ID FAQ at http://www.ainslie.org.uk/callerid.htm
The following code example was posted to the TAPI newsgroup but has not been tested!  
It may also be found at http://www.deja.com/getdoc.xp?AN=398786842&fmt=text


From: "rj@adphone.co.nz" <rj@dontspamme.adphone.co.nz>
Subject: Re: retrieving caller's telephone number
Date: 08 Oct 1998 00:00:00 GMT
Message-ID: <6vgojo$r5o$1@news.wave.co.nz>
References: <361b3931.187097@news.jaring.my>
X-MimeOLE: Produced By Microsoft MimeOLE V4.72.2106.4
Organization: Wave Internet Services
Newsgroups: microsoft.public.win32.programmer.tapi

Here's some code,
Hope it helps


void CTapiLine::GetCallInfo() {
 LPLINECALLINFO lpCallInfo = NULL;
 m_CallerID.Empty();

 if (!m_hCall) return;
 lpCallInfo = I_lineGetCallInfo(lpCallInfo, m_hCall);  // just a wrapper
with some memory allocation stuff.
 if (!lpCallInfo) {
  DebugLog("ERROR CallerID call info unsucessfull");
  return;
 };

 switch(lpCallInfo->dwCallerIDFlags) {
  case LINECALLPARTYID_ADDRESS:
   m_CallerID = (char*)lpCallInfo->dwCallerIDOffset;
   DebugLog(m_CallerID);
   break;
  case LINECALLPARTYID_BLOCKED: DebugLog("CALLERID LINECALLPARTYID_BLOCKED
Caller ID information for the call has been blocked by the caller but would
otherwise have been available."); break;
  case LINECALLPARTYID_OUTOFAREA: DebugLog("CALLERID
LINECALLPARTYID_OUTOFAREA Caller ID information for the call is not
available since it is not propagated all the way by the network."); break;
  case LINECALLPARTYID_NAME:  DebugLog("CALLERID LINECALLPARTYID_NAME The
caller ID information for the call is the caller's name (from a table
maintained inside the switch). It is provided in the caller ID name variably
sized field."); break;
  case LINECALLPARTYID_PARTIAL: DebugLog("CALLERID LINECALLPARTYID_PARTIAL
Caller ID information for the call is valid but is limited to partial number
information."); break;
  case LINECALLPARTYID_UNKNOWN: DebugLog("CALLERID LINECALLPARTYID_UNKNOWN
Caller ID information is currently unknown but it may become known later.");
break;
  case LINECALLPARTYID_UNAVAIL: DebugLog("CALLERID LINECALLPARTYID_UNAVAIL
Caller ID information is unavailable and will not become known later.");
break;
  default: DebugLog("CALLERID DEFAULT unknown caller ID flag");
 };
 LocalFree(lpCallInfo);
};


LPLINECALLINFO CTapiLine::I_lineGetCallInfo(
 LPLINECALLINFO lpLineCallInfo,
    HCALL hCall)
{
    size_t sizeofLineCallInfo = sizeof(LINECALLINFO) + 1024;
    long lReturn;

    // Continue this loop until the structure is big enough.
    while(TRUE)
    {
        // Make sure the buffer exists, is valid and big enough.
        lpLineCallInfo =
            (LPLINECALLINFO) CheckAndReAllocBuffer(
                (LPVOID) lpLineCallInfo, sizeofLineCallInfo,
"lineGetCallInfo");

        if (lpLineCallInfo == NULL) return NULL;

        // Make the call to fill the structure.
        do
        {
            lReturn = lineGetCallInfo(hCall, lpLineCallInfo);
            if (HandleLineErr(lReturn))
                continue;
            else  {
                DebugError("lineGetCallInfo unhandled error: ");
                DebugError(GetErrorText(lReturn));
                LocalFree(lpLineCallInfo);
                return NULL;
            }
        }
        while (lReturn != SUCCESS);

        // If the buffer was big enough, then succeed.
        if ((lpLineCallInfo->dwNeededSize) <= (lpLineCallInfo->dwTotalSize))
{
            return lpLineCallInfo;
        }

        // Buffer wasn't big enough.  Make it bigger and try again.
        sizeofLineCallInfo = lpLineCallInfo->dwNeededSize;
    }
}