Using Class_Crypt_Rsa in VBA to create signature for JWT

Hello - complete newbie to Github so sorry if wrong place to ask question

I am using VBA from Access DB to connect to Docusign API I have successfully done this using their ‘legacy authentication’.

I now have to change authentication to OAuth 2.0 and need to create a JWT

I create the Header, Payload and then need to use a Base64 encoded version of these together with a private key to create the signature part using RSA SHA-256.

The private/public key pair have been generated from the Docusign account
I just can’t seem to make the leap to create the signature part of the JWT

Whilst google-trawling I have come across the following in Github

I think this could be what I need but just can’t quite see how to use it

Is there anyone out there who can show me an example of creating a JWT - would be wonderful if in VBA. Every explanation seems to show making the JWT encoded header, the encoded Body/Payload and then simply says create the Signature by using the first two parts of the JWT, signed with your application’s private key using the RSA SHA-256 digital signature algorithm - so how can I do this in my tortoise-world of VBA.

This is probably completely the wrong platform but having found the reference to Class_Crypt_Rsa on Github perhaps there is someone

Fingers crossed.