Yep, it's possible, I did it before, you have to download the ICQ api: http://www.icq.com/api/

The examples provide will get you started, you can make the message dialog appear, and you can then use the GetWindow and GetWindowEx api to click the send button, it's not that hard, be sure to read the documentation provided in the ICQ api, these will help you.

Unfortuanatly I deleted my sample project but I'll be willing to help you if you need me to (ICQ me if you need me)

Have funnn!