Custom field validation

Hello

I’ve created a custom field using the instructions in the recipe blog but can’t get a grasp of how to validate to make sure a user selects one of the options.

I’ve registered the field name and name with *

wpcf7_add_form_tag(array( 'radioimage', 'radioimage*'), 'radioimage_handler', array( 'name-attr' => true ) );

Adding this filter didn’t seem to work:

add_filter( 'wpcf7_validate_radio', 'radioimage_validation_filter', 20, 2 );

My objective was to include an image with each item in a set of radio buttons, but want to make this field required. Can someone help?