How to pass custom header via URLDownloadToFile Function

Hello,

I need example on how to pass custom header in URLDownloadToFile function

So far I know I should use IBindStatusCallback interface as someone on other forum posted:

Quote:

Write a COM object implementing IBindStatusCallback, IServiceProvider
and IHttpNegotiate. Have IServiceProvider::QueryService return
IHttpNegotiate when queried for it. Pass IBindStatusCallback off this
object as the last parameter to URLDownloadToFile. Provide your headers
in IHttpNegotiate::BeginningTransaction.

This was an answer for someone who was looking on how to change HTTP-Referer.

What I need to do is pass custom variable in header like variable_xyz=123

But I don't know how to implement it in FASM, help much appreciated!