Thanks to everyone for the help, I got my answer by looking at the peachw.tlh file, it had the values needed. I simply looked at the following declaration and found that number 17 was the inventoryitemslist I needed.

enum PeachwIEObj

{

   peachwIEObjVendorList = 0,

   peachwIEObjPurchaseJournal = 1,

   peachwIEObjPaymentsJournal = 2,

   peachwIEObjPurchaseOrderJournal = 3,

   peachwIEObjCustomerList = 4,

   peachwIEObjSalesJournal = 5,

   peachwIEObjCashReceiptsJournal = 6,

   peachwIEObjSalesTaxCodes = 7,

   peachwIEObjSalesOrders = 8,

   peachwIEObjSalesTaxAuthorities = 9,

   peachwIEObjCompanyInformation = 10,

   peachwIEObjAccountingPeriods = 11,

   peachwIEObjDefaultAccounts = 12,

   peachwIEObjElectronicBanking = 13,

   peachwIEObjChartOfAccounts = 14,

   peachwIEObjGeneralJournal = 15,

   peachwIEObjGeneralLedgerRows = 16,

   peachwIEObjInventoryItemsList = 17,

   peachwIEObjAssembliesJournal = 18,

   peachwIEObjAdjustmentsJournal = 19,

   peachwIEObjShippingMethods = 20,

   peachwIEObjItemTaxTypes = 21,

   peachwIEObjJobList = 22,

   peachwIEObjPhaseList = 23,

   peachwIEObjCostCodeList = 24,

   peachwIEObjEmployeeList = 25,

   peachwIEObjPayrollJournal = 26,

   peachwIEObjTimeTicketRegister = 27,

   peachwIEObjExpenseTicketRegister = 28,

   peachwIEObjCustomerDefaults = 29,

   peachwIEObjVendorDefaults = 30,

   peachwIEObjInventoryItemDefaults = 31,

   peachwIEObjJobDefaults = 32,

   peachwIEObjBillOfMaterials = 33,

   peachwIEObjWorkTicket = 34,

   peachwIEObjUnitMeasure = 35,

   peachwIEObjNumberOfObjects = 36

};