The easiest solution is not necessarily the best solution. When writing programs you have to consider the "stupid users" factor by making your program as non-breakable as possible. Murphy's Law -- if anythihng can go wrong, it will. Don't expect averyone to enter perfect data -- when testing your program you have to now only test the the right data but also the wrong data. Make an effort to see what breaks your program then make changes to guard against it.
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 ...