当用户复制和粘贴内容时，如何检查复制数据与禁止输入？

I am developing one application that has form builder inside it to build the form. In that, i have considered special character '#' & '[]' for backend data processing against form & so i have banned user from typing the key buttons on keyboard for the respective characters too. Thing is i am done with banning user from typing so but if user copies the content from somewhere & paste into the place which supposed to contain above characters the i want to check before user pastes, the data against banned inputs. My concern is this but dont know how to do it or is it possible to do so or any other way to resolve this issue???I am developing one application that has form b