I am trying to pass IR codes from a database program to girder to try and hopfully find missing discrete IR codes for my TV. Could you provide more information on your API. Could your DLL be a COM server.
You can email me at support@usbuirt.com for the API. However, an easier approach for you (since this appears to be a temporary task) is to request (via email) a simple command-line app which you can use to send codes to the USB-UIRT.