Zoho Invoice Line Items are Creator subform lines

Zoho Invoice Line Items are Creator subform lines

Hi There
I'm developing an Invoicing app in Zoho Creator. It will take data from Zoho Creator forms and push it to Zoho Invoice for Invoice generation via Integration tasks of Zoho Creator with Zoho Invoice.

My Invoice line items are entries of a subform named 'Food' in the main form Named "Food Inventory". I've declared a map variable that holds values for each line of subform.

  itemsList = List:Map();
  itemsList.add({ "ItemName" : row.Food_Item, "ItemRate" : row.Rate, "Quantity" : row.Quantity });

My problem is : I'm unable to access itemsList  Map Variable in the main form .When i try to Generate Invoice using this

Invoice_Detail_Status=zoho.invoice.createdraft({ "CustomerName" : input.Store, "Items" : itemsList, "PONumber" : input.PO }).toString();

How should I go ?Please help.