How to create a 'Submit AND Subscribe' button?

Can I do this in post.php to create a 'Submit and Suscribe' button?

<input type="submit" name="submit" value="<?php echo $lang_common['Submit AND Subscribe'] ?>" tabindex="<?php echo $cur_index++ ?>" accesskey="s" onClick=document.thisform.subscribe.value=1/><input type="submit" name="preview" value="<?php echo $lang_post['Preview'] ?>" tabindex="<?php echo $cur_index++ ?>" accesskey="p" />

I added the onclick handler: onClick=document.thisform.subscribe.value=1