See example on here >> https://www.themepunch.com/faq/slide-change-based-mousewheel/ or http://173.254.28.169/~greenbo4/greenbox/project/

Mouse wheel event on slider function.js

var slider = $('#work-carousel'); // Add yoru slider id here

slider.on('mousewheel DOMMouseScroll', function(event) {
 event.preventDefault();
    if(event.originalEvent.wheelDelta > 0 || event.originalEvent.detail < 0) {

        slider.slick('slickPrev');

    }
    else {

        slider.slick('slickNext');

    }

});