Code only works if I add Extra character

Question

Hi, so there's a bit of code I use to keep a running list of pages I need to print (puts it in a textbox), solely depending on if certain boxes are checked... Say I have 3 checkboxs, and each represents a certain page or pages to be printed...  If select each of those checkboxes, pagesToPrint (a textbox) will be populated with 9-11, 15-40, 43 of the PDF (I made up the page numbers).  If I unselect one of those checkboxes, I need the value to be removed from pagesToPrint.  So pagesToPrint should read something like 9-11, 15-40.
The code I'm posting below WORKS, except that I have an issue having the text to remove itself from pagesToPrint when the input is just a single number AND when it's the first item in the box... Example: "43" won't remove from pagesToPrint when I unselect the textbox txt1; but if I changed it to "43 " (added space at the end), "43-44" or "43a" all would work.  So if the box read 43, 9-11, 15-40 (the integer only being first) then the 43 wouldn't remove if the corresponding checkbox were unselected.... If it were populated with 9-11, 15-40, 43 (the range being first) then the 43 would remove if the corresponding checkbox were unselected
Why is that??
// script start - Trying to debug a removal issue on txt1 when integer lacks a space, symbol, or letter
//get the button
var btn = this.getField("txt1");
//app.alert("value = "+btn.value);
// this variable would change for each check box to the pages you want printed.
var pagesToPrint = "43";
//check value of checkbox
if(btn.value=="Yes") {
  var action = "add";
else
  var action = "";
updatepagesToPrint(pagesToPrint, action);
function updatepagesToPrint(pagesToPrint, action) {
  //app.alert(pagesToPrint + " :: " + action);
  // get the text field
  var printField = this.getField("pagesToPrint");
  if(action=="add")
  // check if the field is empty
  if ( printField.value == "" || printField.value == " ")
      printField.value = pagesToPrint;
  else
      // as printField has a value, add the new pages to the end of the value
      printField.value = printField.value + ", " + pagesToPrint;
  else
  printField.value = printField.value.replace(pagesToPrint+", ", "");
  printField.value = printField.value.replace(pagesToPrint, "");
  printField.value = printField.value.replace(/^,|^, |, $|,$/, "");
// script end

Answer 1

http://s000.tinyupload.com/?file_id=07374325820103346475
Try to check and uncheck DI change request FIRST.... It stays, when it should delete... Any other order it works.  It must be "89a" or "89-110" or "89 " to work.
If you check the boxes in any other order, it works perfectly.