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How do I tell in MT4 that historic data has actually been loaded from the server? I already have code that is supposed to do that and checks for ERR_HISTORY_WILL_UPDATED, but apparently MT4 doesn't return this code EVEN if there is NO backdata loaded from the server, as is the case when starting the EA for the first time at a broker for example, or if the the client hasn't connected to the server for a while (incomplete data). When I restart/reload the charts the data is there, but that's not good enough as the EA *MUST* know whether it has all the relevant data or not. For reference here is the part of the code that checks this:

for(int p=PERIOD_MN1; p>0; p=PeriodLower(p)) {
  GetLastError();
  ArrayCopyRates(data,symbol,p);
  if(GetLastError()!=ERR_HISTORY_WILL_UPDATED) Print("Historic data on ",PeriodToString(p)," up to date (",iBars(symbol,p)," bars, first on ",TimeToStr(iTime(symbol,p,iBars(symbol,p)-1)),")");
  else {
    addComment(PrintLog("Updating historic data on "+PeriodToString(p)));
    hist_updating++;
  }
}

As I said, for some reason even if there is no data loaded from the server, ArrayCopyRates doesn't report ERR_HISTORY_WILL_UPDATED.

So, to repeat the question, how EXACTLY to tell whether historical data for a particular symbol and timeframe has been loaded or not from the server AND potentially force an update?