Ed should emphasize that Ancient Dragon was talking about the binary value of a long int, not the character representation. A lot of times when people want to "cast" a string to another type they really mean a string conversion rather than a real cast:
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 ...