How to validate site key and secret key?

I need to validate if the two keys entered in a cms settting web form are valid. I know I can do this with http://bit.ly/11H4Jer link and secret key, but there is no error code for site key. How can I verify the site and secret key without adding a captcha to the settings page? -- You received this message because you are subscribed to the Google Groups "reCAPTCHA" group. To unsubscribe from this group and stop receiving emails from it, send an email to recaptcha+unsubscribe@googlegroups.com. To post to this group, send email to recaptcha@googlegroups.com. Visit this group at http://bit.ly/1dkFnYd. For more options, visit http://bit.ly/P65DvS.