Identifying Loop Textbox

i created my texbox in a while loop. that means when the texbox is displayed with the questions that come from the database it has the same name. how do i differentiate this textbox from the others.

i know i have to assign some variable to it but how do i do it? there is also a button at the end of the page that check the values in each textbox with that of in the database. basically the page displays lessons where the questions are retrived from the database. and its a fill in lesson.