finding the control which is in gridview globally

Hi,

 Globally i want to find a textbox which is in a gridview such that i can use that variable in any of the events.

    Is that possible in .cs file
          or
 if not how can we retreive the variable of a textbox in to a function after finding the textbox using javascript in .aspx page .

I tried to find a control in .cs file but I couldn't get it.
Please, give the solution.