Nadya,

>Should I call thisform.refresh or it would be enough to call thisform.txtMsg.refresh()?

You can .Refresh() just the textbox, you can encapsulate everything in a method call.

>The strange thing is, that it worked fine before without refresh(). Also if I click once on this control, all other messages are updated correctly during the execution of the form...

because the textbox has focus it'll update on the screen whenever the .Value changes.