How to update custom field for each invoice item by deluge ?

How to update custom field for each invoice item by deluge ?

I have below code to try to update custom field named "Com".
When I run it, I get this error message
"{"code":15,"message":"Please ensure that the invoice_items has less than 100 characters."}"

The reason I tried this way is because I didn't find how to update only "Com" custom field for each item on invoice.
It's best If I can update only that field. (Please let me know If you know this way) but I couldn't find it.
So I just get all invoice_items field and then add new custom field inside then try to update but I get characters limit error.

Please help me if you know how to solve this issue.
Thank you.

  3. invoiceID = invoice.get("invoice_id");
  4. organizationID = organization.get("organization_id");
  5. salesperson_name = invoice.get("salesperson_name");
  6. invoice_items = invoice.get("invoice_items");
  7. custom_fields = invoice.get("custom_fields");
  8. sale_type = "";

  10. for each  item in custom_fields
  11. {
  12. label = item.get("label");
  13. if(label == "Sale Type")
  14. {
  15. sale_type = item.get("value");
  16. }
  17. }
  18. invoice_items = invoice.get("invoice_items");
  19. new_invoice_items = List();

  21. for each item in invoice_items
  22. {
  23. item_custom_fields = item.get("item_custom_fields");
  24. type = "";
  25. for each  item2 in item_custom_fields
  26. {
  27. label = item2.get("label");
  28. if(label == "Type")
  29. {
  30. type = item2.get("value");
  31. }
  32. }
  33. product_name = item.get("name");
  34. splitProductname = product_name.toList("-");
  35. commision_detail = zoho.crm.searchRecords("commsions_structure","(Staff_Member.name:equals:" + salesperson_name + ") and (Product.name:equals:" + splitProductname.get(0) + ") and (Sale_Type:equals:" + sale_type + ") and (Type:equals:" + type + ")");
  36. if(commision_detail.size() > 0)
  37. {
  38. commision = commision_detail.get(0).get("Commission");
  39. }
  41. CustomField = Map();
  42. CustomField.put("label","Com");
  43. CustomField.put("value",5);
  44. item.put(CustomField);
  45. new_invoice_items.add(item);
  46. }

  48. test = List();
  49. test.add(new_invoice_items);

  51. values = Map();
  52. values.put("invoice_items",test);

  54. response = zoho.invoice.update("Invoices",organizationID,"3878353000003769092",values,"zohoinvoice");
  55. info response;