Setup flag in Javascript

Below is a script I am using for a Google Docs Spreadsheet.

These links show what I am doing:

http://i.stack.imgur.com/uGik7.png

http://i.stack.imgur.com/AbKnQ.png

How can I set up a "flag" so that when I run this script a second time, it doesn't add the perviously added stock items?

function myFunction() {
  var ss = SpreadsheetApp.getActiveSpreadsheet();
  var sheet1 = ss.getSheetByName("Purchase Orders");
  var sheet2 = ss.getSheetByName("Inventory");
  var data = sheet1.getDataRange();
  var i_data = sheet2.getDataRange();
  var lastRow = data.getLastRow();
  var iLastRow = i_data.getLastRow();

  for (i=1;i<=lastRow;i++) {
    if (data.getCell(i, 5).getValue() == "stock"){
      for (n=1;n<=i开发者_如何学CLastRow;n++){
        if (data.getCell(i,3).getValue() == i_data.getCell(n,3).getValue()) {
        i_data.getCell(n, 1).setValue(i_data.getCell(n,1).getValue() + data.getCell(i,2).getValue());
       }
      }
    }

  }
}​

I guess I'm trying to do this: Once the item has been added to inventory, the script adds an x to column i of that line. Then when the script is run again, it skips over the lines with an x in column i

Designate a cell to hold the flag value, and have the script check that particular cell for the flag value.

In JavaScript, functions are objects. Objects have properties. So, decorate your function:

function myFunction() {
    if (!myFunction.alreadyDoneRunIt) {
        alert('bapt uia');
        myFunction.alreadyDoneRunIt = true;
    }
}

for (var i = 0; i < 10; i++) {
    myFunction(); // alerts once
}