Uploading csv file with vba

I am trying to upload a csv file to an api without any success. I have been able to upload a single data record via Fiddler so I know the api is working. The limited information from the api is below. Would anyone please have any idea how I code this in vba?

UPLOADING FILES
When uploading files for the create, update or delete actions, in default mode the API expects the data in multipart/form MIME format via a HTTP POST request, with the input file marked with an dxi name field. For example in a basic HTML form this would look something like the following:

<form name="myform" enctype="multipart/form-data" action="https://api.dxi.eu/database.php?action=create&format=xml" method="POST">
<input type="hidden" name="method" value="{method}">
<input type="hidden" name="token" value="{token}">
Send this file:<input name="dxi" type="file">
<input type="submit" value="Send XML File">
</form>

The API accepts input files in XML, JSON or CSV format using plain text (ascii) or UTF-8 encoded data. The API does not accept data in UTF-16 encoding.
To assist in uploading large data files or connections over slow links the uploaded files can be compressed as .zip, .gz or .bz2 formats. The uploaded filename must have the appropriate file extension for the API to detect if compression was used.