There are ways you can get around this.
- The calculations can be done in javascript, which happens in the browser
- You can make an ajax call to the server to perform the calculation and return the result. The page will not be reloaded.

>I am probably obsolete, but I understand that web servers start each response somewhat ignorant of the state of the screen. Some of our main screens are kind of data dense. They are not just data capture and process later. They provide continuous feedback of calculations as data is entered. That is valuable from the customer's point of view.

If your application is written in VFP, you will need to run on a Windows server so you will be doing COM interop from the server to the VFP COM component. Read everything you can that Rick Strahl has written about this. My guess though is you will get significant improvement by rewriting so you don't have to go through the COM interop stuff.

You should also be aware that Microsoft has open sourced their entire web stack and is in the process of open sourcing the .Net core (server components). They are both mature and improving all the time.

>I know that, but our app's exe is 50 MB and we cant afford to have to rewrite stuff that already works except for significant improvement, so we are looking for that sweet spot where the tool is improving yet mature, or at least committed to keeping old code working, as has been the case with VFP.