If you want a simple function to update the item purchase price to the latest bill received then you can use the following to accomplish this....

billItems = bill.get("line_items");

for each line in billItems

{

rate = line.get("rate");

id = line.get("item_id");

res = zoho.books.getRecordsByID("items",organization.get("organization_id"),id);

item = res.get("item");

rateNow = item.get("purchase_rate");

if(rateNow != rate)

{

myMarkup = 1.5; // this is your markup if you want to amend the sales price by a margin of the buying price - replace the 1.5 with your choice

newSellPrice = rate * myMarkup;

newRate = Map();

newRate.put("purchase_rate",rate);

//newRate.put("rate",newSellPrice); // un-comment this if you want to amend the sales price

result = zoho.books.updateRecord("items",organization.get("organization_id"),id,newRate);

}

}

If you're struggling to set this custom function up then let us know - we'll walk you through it !