How to get Trading House Listing data

[cabwav]

I am rather new to AddOn development. I would like to write Trading House listing data to SavedVariables so that I can process these listed items outside ESO in order to keep track of what I listed for sale.
I am a member of two Guilds: one is my 'regular' guild that has no trader, and the other one is the Trading guild that I use for selling things. I am using this code:

for j = 1, GetNumGuilds() do
        local guildId = GetGuildId(j)
        if (SelectTradingHouseGuildId(guildId)) then
            local currentListingCount, maxListingCount = GetTradingHouseListingCounts()
            if(currentListingCount > 0) then
                for i = 1, currentListingCount do
                    local _,itemName,displayQuality,stackCount,_,timeRemaining,salePrice = GetTradingHouseListingItemInfo(i)
                    local link = GetTradingHouseListingItemLink(i,j)
                    local linkItemId = GetItemLinkItemId(link)
                  table.insert(mytable,string.format("%s;%s;%s;%s;%s",guildId,linkItemId,itemName,salePrice,timeRemaining))
                end
            end
         end
      end

This returns a table that contains twice the number of items, exactly the same for each guild although one of the guilds has no sellable items. What am I missing here?

The above code only works when I visit the bank, and open the listing from the guild trader.
Is there a way to access the listing data in the bank without actually visiting the bank?

Thank you in advance