how to add expiry date with password to one .mq4 formula ??

1. You have only three choices: Search for it, learn to code it, or pay someone. We're not going to code it FOR you. We are willing to HELP you when you post your attempt (using SRC) and the nature of your problem.
2. Since any protection you add to the mq4 can be easily decompiled (until Upcoming MetaTrader 4 and MQL4 Upgrades - Big Changes Are Underway) why bother?
   

thanx for ur suggestion... during my search i found one code..but i dont know how to link to the existing code .. can i get some knowledge on this ??

You can Hardcode the Date && Password. Then allow inputs with extern variables.

hii Ubzen... any examples.. no idea on this ..

I dunno what I was thinking when I responded. If you're concerned about de_compilation protection then the below will-not help. Anyways below is what I had in mind when I responded. Like WHRoeder said, hope the new version offer better protection.

extern int Password=0; //Correct Value=55665566

void start(){
    bool Expire=TimeCurrent()>StrToTime("2013.11.30 00:00");
    if( Expire && Password != 55665566) return;
    ..................
    ...happy...demo...
    ..................
}

//+------------------------------------------------------------------+
//|                                                  Protect-005.mq4 |
//|                                Copyright © 2009, Sergey Kravchuk |
//|                                         http://forextools.com.ua |
//+------------------------------------------------------------------+
#property copyright "Copyright © 2009, Sergey Kravchuk"
#property link      "http://forextools.com.ua"

int start()
{  
  string char[256]; int i;

  for (i = 0; i < 256; i++) char[i] = CharToStr(i);

  // Date, until which the expert is allowed to work
  int LastAllowedDate = StrToTime(
  /* 2009.09.11 23:59:00 */ 
  char[50]+char[48]+char[48]+char[57]+char[46]+char[48]+char[57]+char[46]+char[49]+
  char[49]+char[32]+char[50]+char[51]+char[58]+char[53]+char[57]+char[58]+char[48]+char[48]

  ); 

  if (TimeCurrent() >= LastAllowedDate) 
  {
    Print("Demo period has expired " + TimeToStr(LastAllowedDate,TIME_DATE|TIME_SECONDS));
    return(1);
  }
  
  Print("You can work until "+ TimeToStr(LastAllowedDate,TIME_DATE|TIME_SECONDS));
}

while searching i found this code.. bt no idea how it will work .. as when i try to put this formula to a chart then it wont come .. any suggestions ???

If you are looking to sell your EA/Indicator/Script at least learn to code so you can give your customers a semi-reasonable product.

thanx for ur valuable suggestions.. bt why it is nt working ..