Set Item Vendor Purchase Price

Attempting to set the purchase price for a vendor on an inventory item. The script executes without error but, does not update the price. Here is my function, can anyone clarify the steps to correctly save the purchase price?

function SetVendorPrice(ItemId, VendorId, VendorPrice)
{
    var ItemRecord = nlapiLoadRecord('inventoryitem', ItemId);

    var VendorCount = ItemRecord.getLineItemCount('itemvendor');
    for (var i = 1; i <= VendorCount; i++)
    {
        ItemRecord.selectLineItem('itemvendor', i);

        if (ItemRecord.getCurrentLineItemValue('itemvendor', 'vendor') == VendorId)
        {
            ItemRecord.setCurrentLineItemValue('itemvendor', 'purchaseprice', VendorPrice);
            ItemRecord.commitLineItem('itemvendor');
        }
    }

    nlapiSubmitRecord(ItemRecord, false, false);
}