problems with setting a radiobutton to checked thats inside repeater.

Hello and thanks for reading.
I have a repeater that contains some controls including 5 radio buttons.
To explain it fast: I made a huge survey site and In case that the site crashes or something and the user has to redo the test. I would like it to check if there is already an answer in the database from the current user. Hope it makes sence.
private void GetOldAnswers() { Label QuestionID = (Label)lstQuestion.Items[0].FindControl("QuestionID"); int questionID = Convert.ToInt32(QuestionID.Text); int userid = Convert.ToInt32(Session["UserID"]); RadioButton rb1 = (RadioButton)lstQuestion.Items[0].FindControl("Rb1"); RadioButton rb2 = lstQuestion.FindControl("Rb2") as RadioButton; RadioButton rb3 = (RadioButton)lstQuestion.Items[0].FindControl("Rb3"); RadioButton rb4 = (RadioButton)lstQuestion.Items[0].FindControl(&quo ...