Catch Runtime Index of Control

Question

am using C#, VS-2005

If we provide the Index of textbox on runtime like below

TextBox Tb=new TextBox();

tb.Name= "Tbox"+ i.tostring();

and get the last Index of Textbox like below.

Foreach(Control ct in panel1.controls){

if(ct.Name.Contain("Tbox" + i.tostring() && ct is TextBox){

Int index= ct.name.length-1;

if the last index we get from textbox then how to call it in specific condition like to set focus on another control.

thx In Advance.