design a licence management dll for existing exe for online verification

Job ID: 32504381

Budget: ₹1,500 – ₹12,500 INR

I have an exe and I already lost the source code.
I want to pack the exe with a custom dll (which needs to be designed) and use use it to manage subscriptions (monthly/yearly) to the software.
The licence will be stored locally as well as on my server. If the user is offline, the local licence will be used but if the user is online, the server stored licence will be used. The first time activation should be online only though.