Is possible to detect winapi calls?

[fonx]

Hi everyone. I'm .net developer but for winapi purposes this subforum is ok. Please excuseme if my english isn't perfect, however I think I can express the main idea. My question is the following:

I developed an application(let's call app1) that gets information from a second application (let's call app2) by using winapi calls: (gettext, settext, capturing screenshoots of the app2, mouse events,...). Can app2 notice these winapi calls?

Thanks for the responses, kind regards.

[golanshahar]

You can do it using API Hooking look at this article (http://www.codeguru.com/Cpp/W-P/system/misc/article.php/c5667).

Cheers

[fonx]

Hi Golan :), I'm glad about your help, I got from you most of my winapi knowledge that I used to make my application.

From your response I suppose that winapi calls can be noticed by the target application, right?

What happens with API Hooking? Is Hooking totally invisible? I'll take a look in the article at home (i'm at work), but it seems very interesting. The bad thing is having to code again my application from WinAPI calls to API Hooking...