Enable button after checking 3 checkboxes

[samuemx]

Hello,

I´ve a list with 10 checkboxes and I as wondering if there are any way of enable a submit button only when 3 of them are checked.

I've this code but it enables de button if any checkbox is checked.

<script type="text/javascript">
function enviar(){
    document.form.aceptar.disabled = true;
    for (i=0;i<document.form.elements.length;i++){
        if(document.form.elements[i].type == "checkbox"){
            if(document.equipo.elements[i].checked == 1 ){
                document.form.aceptar.disabled = false;
                
            }
        }
    }
}
</script>

Any clue would be great!