Detect mail from ah

[Tntdruid]

Hello,

first my code:

function Accountant_DetectAhMail()
    local numItems = GetInboxNumItems()
    local invoiceType = GetInboxInvoiceInfo(numItems)
    if invoiceType == "seller" then
    auditorMode = "AH";
        else
    auditorMode = "MAIL";
    end
end

I'm trying to Detect if the mail is from a succesfull auction, it never return the AH or MAIL, i'm still new to lua stuff, been looking at
http://wowprogramming.com/docs/api/GetInboxInvoiceInfo
http://wowprogramming.com/docs/api/GetInboxNumItems