How to add DYNAMIC Header values before Posting the HTTP request to server

I have a .net REST API for fetching the data from the database.

It is using JSON to POST the requests.

In the Request Body we pass the required parameters and in Headers we pass the Security token along with other parameters.

This Security Token will change every time for each request, Posted to the server.

 

I have the DLL which has the logic of generating the security token.

The Problem is -> How can i use this DLL so that, EACH time when i run the script from VUgen, it will ADD the Security token parameter in the HEADERS and After that POST the request body.

It is something like (in simple words) - When we run the VUgen script -> The DLL methods will add the Security Token parameter in the Headers and THEN, the Scripts execution will proceed with this security token and Post the request to server.

 

Could you please let me know, if it is possible to ADD the security token in the PRE Request ?

Note - VUgen script i have created using the Fiddler's .SAZ file and it contains the web_custom_request() method

Thanks.