Make page invalid in server code

I am creating forms from code that include checkboxes and there is no validator that can make sure a checkbox is checked on its own like existence and compare validators can. Checkboxes need use custom validators which will not work for me because the checkbox id is arbitrary and there can be any number of them with any number requiring the check. I  can get a custom validator to call a server function but it does not know and cannot reference the field checkbox data since everything is done on the fly.  The HTML page is just a div that I add the code generated form too.
I manage the data in my form by reading the posted form data. To complicate everything,  an unchecked checkbox does not put a value in the form data so I must check for its non-existence to know it is not checked. I have all this working fine except for the validation status.  I know which checkboxes are not valid and I have added my own validation message to the form and the vali ...