You may check out that are there any kind of signals that are generated and can be handled when a text file gets updated....if yes, then you can use signal handling and make your program wait until a signal is received and then process the data in file....that will definitely reduce your CPU usage...
For Each ctrl As Control In Me.Controls("pnlMainPanel").Controls
If ctrl.GetType Is GetType(System.Windows.Forms.Panel) Then
For Each subCtrl As Control In ctrl.Controls
If subCtrl.GetType Is GetType(System.Windows.Forms.TextBox) Then
If subCtrl.GetType Is ...