Take Classic ASP
out of the mix for the time being, as what you are looking for at first will be what is on the HTML page the end user sees, and I think you are on the correct track with utilizing AJAX to accomplish this.
I have seen similar done using the onblur
event attached to the input
elements. Basically anytime a field loses focus it will fire a JS routine grabbing the field's name/value as well as the FormID (your ACode) and then submitting that information via an AJAX call.
All of this should be relatively easy to find samples for.
Now the Classic ASP is the other half of your equation. There is a lot of documentation out there for this as well, but it can be difficult to find as "Classic ASP" wasn't the name for this until a few years after ASP.NET was released.
As I did plenty of the Classic work in my youth.... I do remember what site that I frequented (besides here) and learned quite a bit about VBA/Classic ASP and how this all worked. They still have a good long list of articles from the late 90s which should give you plenty of information to start with.
Active Server Pages Index - 4GuysFromRolla.com
Now once you get to a specific problem that you are having implementing this, feel free to come back and ask for help. While someone may not write out the solution for you, there are plenty of people here who can help you with the bad line of code here or there types of issues