Message validation

Hello,
Is it possible to add additional message validation to the form?
I want the form to throw an error if the message contains a URL. For my other sites, which use contact form 7, it uses the ‘Disallowed Comment Keys’ field in the Discussion settings of WordPress and for sites using gravity forms I have used a filter to hook into field validation as shown below.

Is it possible to do something similar with this form plugin?

Thanks

Jo

Gravity forms validation:

// add custom validation to form
add_filter( 'gform_field_validation_1_4', 'validate_1_4', 10, 4 );
function validate_1_4( $result, $value, $form, $field ) {
    $nourl_pattern = '(===|http|https|www)';
    if ( preg_match( $nourl_pattern, $value ) ) {
    $result['is_valid'] = false;
    $result['message']  = 'Message can not contain special characters or website addresses.';
}
return $result;
}