how to get textbox value from a gridview control in webpage

Question

how to get textbox value from a gridview control in a webpage programmed in asp.net 2.0 C#

i am doing a forum 

in the forum i have texbox in gridview control in forum page

how to get the textbox value in a string so as to check the same value with the DB

i have tried like below but no use

string Ques = (TextBox)GridViewFRM.Rows[i].Cells[0].FindControl("GVQuestionTextBox");