Please tell him that he can come back ____ _____ _____ _______.请告诉他什么时候想回来就回来.

any time he likes能不能填：whenever he would like用would好像没有什么道理，去掉would，则很难凑成四个单词would like和 want一样都是想要呀根据前半句，这里不能使用would，不适合使用虚拟语气，而应使用一般现在时。