如何将从其他程序点击的文本导入您自己的文本框？

What I mean is how can I get text from another running active window. For example I have a program let's say word or msn. I am chatting with someone while my own program is running in the tray. I want to set a key let's say right click and ctrl to open up my program and get the word I clicked on. I am using C#.What I mean is how can I get text from another