[Rilgamon]

what sezz says is true. I dont have the trader so I cant test but I highly doubt it works.
The code to do it would look like this ...

function stock:BAG_UPDATE_DELAYED()
    if(not MerchantFrame or not MerchantFrame:IsVisible()) then return end
    local bag = 0
    while(bag<=NUM_BAG_SLOTS) do
        local slot = 1
        while(slot<=GetContainerNumSlots(bag)) do
            if(C_NewItems.IsNewItem(bag, slot)) then
                local item = ItemLocation:CreateFromBagAndSlot(bag, slot)
                local itemLink = C_Item.GetItemLink(item)
                local itemName, itemLink, itemRarity, itemLevel, itemMinLevel, itemType, itemSubType, itemStackCount, itemEquipLoc, itemTexture, itemSellPrice, itemClassID, itemSubClassID, bindType, expacID, itemSetID, isCraftingReagent = GetItemInfo(itemLink)
--              print(itemName, itemType, itemSubType, itemClassID, itemSubClassID)
                if(itemClassID ~= 7) then -- dont sell crafting reagents
                    UseContainerItem(bag, slot)
                end
            end
            slot = slot + 1
        end
        bag = bag + 1
    end
end