The sideload command is available through the C# Flat SDK. You can reference the compiled DLL and it will appear as a library in VB.Net.
You can download the C# Flat SDK at: http://developer.nirvanix.com/files/folders/reference_code__applications/entry692.aspx
To call the sideload command you create an IMFS object and call sideload with targetUrl, destinationPath, and if you have a callback handler the callbackURL.
Regards,
Barry R.