sql error help

hey everyone, i am trying to output this query in html through javascript. the error it gives me is error # 2147217913 error converting datatype nvarchar to numeric

code: var ItemCode;

ItemCode = window.prompt ("enter items lookup code"," "); var sql = "SELECT [Transaction].Time, [Transaction].TransactionNumber, TransactionEntry.Price, TransactionEntry.Quantity, Item.Description FROM TransactionEntry INNER JOIN [Transaction] ON TransactionEntry.TransactionNumber = [Transaction].TransactionNumber AND TransactionEntry.StoreID = [Transaction].StoreID INNER JOIN Customer ON [Transaction].CustomerID=Customer.ID LEFT JOIN Item ON TransactionEntry.ItemID = Item.ID LEFT JOIN Store ON TransactionEntry.StoreID = Store.ID"; sql = sql + " WHERE Item.ItemLookUpCode = " + ItemCode;

any help will be much appreciated