necessary changes

First, I congratulate the authors of the plugin.

I have this questions, and i hope that can you help me:

1) I need that, if the visitor of my site has not selected the tag “[acceptance]”, the plugin (when the visitor push the button”send”) must indicate with a messagge of error that the tag “[acceptance]” not selected, and if the tag will not be selected the messagge can’t be sent.

2) I need that, when the visitors of my site press the button “send” the plugin redirect in a other page.

http://wordpress.org/extend/plugins/contact-form-7/