> "program to swap two no. using third variable"
A better question would be:
"How to swap my idiot teacher of 1970's assembler tricks with someone who has a clue about programming in the modern world".
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 ...