While this is possible in theory, I would not recommend it. The default way Pega behaves is that values from text controls are committed to the clipboard in the OnChange event, and this event typically occurs on a focus change. Rethink your use case - why do you need to show/hide this button in the first place?

If there really is no way around it, here's how I would approach it. The general idea is as follows:

1. A visibility condition controls whether the button is visible or not
2. Every time the text changes, commit this value back to the Clipboard
3. In addition, a section containing the button is reloaded each time.

Note: it is imperative that the button is not contained within the same section as your text control, otherwise the cursor would be moved to the very beginning whenever the user types something.

Create a new section and embed it in your view. Add your button, and create the following visibility condition:

The condition itself is pretty straight-forward. Let's say your field is called Name:

Then, on your text control, create an action using the Any key event. Add a Post value and a Refresh-Other section action:

Save your work. Here's the result:

Again, I would NOT recommend this. Pega commits the value back each time your user types something.