function poboxcheck() {
	
//  var regexvalue = "(?i)^((?<!P\\.?\\s?O\\.?\\sBox).)+(?<!P\\.?\\s?O\\.?\\sBox)$";
//use this rx:
  var regexvalue = "^(P\\.?\\s?O\\.? Box)";
//  var re = new RegExp(regexvalue);
//and this way to call regexp:
  var re = new RegExp(regexvalue, "i"); //the "i" modifier makes it case insensitive

  if ($('SID1_Street').value.match(re)) {
    alert("You can not use PO Box Address for Physical Addresses.  Please use your physical address.");
	return false;;
  } else {
    alert("No match");
  }
}