I purchased Internet Download Manager several years ago, and it has been updated many, many, times as browsers have evolved/changed. IDM is able to intercept most, but not all, download activities from within Chrome when you set the IDM preferences to integrate IDM into Chrome.
The fact that IDM is frequently updated
just to deal with Chrome integration, and the fact that IDM has user-preferences for selecting integration with any/all of seven different browsers, suggests that hooking Chrome at a low-level is probably a major technical accomplishment, and may require frequent updates of your code if you are able to hook into it.
As an alternative, how about setting the browser default download path to a special folder you create which your application has created a FileSystemWatcher to monitor, and then detecting the addition of the downloaded file ?
For example, see John Simmons' two-part CP series on FileSystemWatcher: [
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