<p>How do I implement a Copy menu item in a Windows application written in C#/.NET 2.0?</p>

<p>I want to let the user to mark some text in a control and then select the Copy menu item from an Edit menu in the menubar of the application and then do a Paste in for example Excel. </p>

<p>What makes my head spin is how to first determine which child form is active and then how to find the control that contains the marked text that should be copied to the clipboard. </p>

<p>Help, please.</p>

It seems to me that you might be better off breaking this into smaller tasks/questions.
You have a few issues you are stuck on from the way it sounds.
You have multiple 'child' windows open. Is this an MDI application?
When an action is performed on one of those child windows, it should fire an event in that window's event handlers. That is your first thing to set up. If this is a datagridview I would suggest a simple test to start. Try trapping the
DataGridView.SelectionChanged
event. Just throw in something like
```
MessageBox.Show("I copied your datas!");
```
for now.
This should get you started where you will at least understand how this event will be raised to you.
From here, we will need to know a little more about your datagrid, and the rows and child controls in those rows. Then we can likely create events in the render events that will be raised at the appropriate times, with the appropriate scope.