Javascript confirm if .NET default validators returns true

Hi Experts,
   My page contains some textboxes on each a required field validator is attached , what I want is to call confirm function from javascript if these validators returns true, on the submit button click.
how can this be done?
Following code is written on the onClick server event of the submit button.
which does not works as client script is always runs at the end of C# function code. So I am always getting false(default) value in HiddenField1.Value causing not to execute statements inside if.

wht can be done?

string script = "document.getElementById('HiddenField1').value = confirm('Updating settings,click ok to continue');";
                    ScriptManager.RegisterStartupScript(Page, typeof(Page), "CliIsvalid", script, true);
                    if (Convert.ToBoolean(HiddenField1.Value))
                    {                                          
                        Updatesettings();
                        ScriptManager.RegisterStartupScript(Page, typeof(Page), "CliRedirect", "parent.location.href='logout.aspx';", true);
                    }

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