Is it possible to get list of unique magic number?

It is certainly possible.

The code assumes that the expert has sole use of the trading thread.

double SeqNum() {
  double dSeqNum=1;
  
  if(GlobalVariableCheck("_SequenceNumber")) {
    dSeqNum=GlobalVariableGet("_SequenceNumber")+1;
    if(dSeqNum==1) dSeqNum=-1;
  }
  if((dSeqNum>0) && (GlobalVariableSet("_SequenceNumber",dSeqNum) == 0)) dSeqNum=-1;
  if(dSeqNum==-1) Print("Error ",GetLastError());
  return(dSeqNum);
}

Thanks for the code. I believe you are trying to generate a sequence series. What I need is to get the unique magic numbers from all the orders. Let see I have following magic numbers for open and pending orders

1010

1020

1030

1010

1040

1050

1060

1040

1060

I need to find a way to get unique magic numbers and they are from above

1010

1020

1030

1040

1050

1060

I hope you understand my problem. Thanks for help again

What do the "From" set of numbers refer to, as they are not unique (1010x2, 1020x1, 1030x1, 1040x2, 1050x1, 1060x2)?

Read all the numbers into an array

Sort the array

Read the numbers into another array, ignoring duplicates

You now have an array of sorted unique numbers