Get Cash redemption cheque with customer's points

[Marionlesso]

Hi there, 

Here is a good one, the situation:

We are building a website only accessible to our VIP clients. They can download files, marketing content, buy exclusive products. 
On this website they have access to their points, we installed Rise.ai. They cumulate points from sales outside of this website, someone will upload and updates their points manually every week.

The problematic:
With their points, the clients can also get a cheque. They will redeem their points and we will send them a cheque (1 point = $0.70)
I created a product called cash redemption and I would like my clients to enter the number of points they want to redeem and be able to see the cheque amount.
OR eventually, enter the cheque amount and be able to preview the number of points they need to redeem. 

I'm quite lost and would like to know if anyone knows a solution or an app that could help me achieve that. 
If not, any contact of someone I could hire. 

Thanks,