Hello,
Can you provide a briefing of the existing system? It will be easier for us to understand how to do it. We believe you will provide full source to make the changes or do you want it to be a plugin which you can integrate and can be used later in other systems too. Please clarify so that we can bid accordingly.
We can share few examples of our previous work for reference. If you have any questions or need any clarification, please contact us.
Regards,
OKTeam