Using class validator forbid same item from being present in 2 different arrays

Hello folks I am working on an University project wherein I need to manage the course taken by the students. The application has a form to add course and delete a course sometimes I observe that students are putting same course in “add” list as well as in “remove” list how do I prevent that from happening

Here is my vdliation schema

{ IsOptional, IsArray } from "class-validator";

class courseValidate {
    @IsOptional()
    @IsArray()
    addCourses!: string[]


    @IsOptional()
    @IsArray()
    removeCourses!: string[]
}

I tried various custom decorator but they are not working