have WHMCS give out login's from a text file list ($50 Max)

hello I want to have WHMCS send an email when a product is paid for that includes p remade logins the idea is to add a field like {$client_name} though would be named something like "Pre-made-ProductName" I place that in an email template and it auto inputs the top line from a text file and then deletes that line then in the product that triggered the email it adds the same line here [login to view URL] these text files would be stored in a new folder on the server for easy access and each file would have the same name as the code to be put in the email template "Pre-made-FileName" would be that actual code this needs to be usable for an unlimited number of products by simply adding more files to the folder PS I want this job done inside of $50 so please don't bid over that if no one dose it I may re-post later and pay more but for now this is something I want, not something I need