Comments by Rishi Dahikar (Top 1 by date)

you write the code in Form_Keydown event right so your all textbox having tab index 1,2,3 etc if ur focus on 3 textbox so pressing F1 , focus goes to textbox having tab index 2
just copy and add this code to your form

Protected Overrides Function ProcessTabKey(ByVal forward As Boolean) As Boolean
End Function
and try