What you describe is (1) inability to recall exactly what you asked of him, and (2) loss of "executive" funtion, which limits or prevents him from following "complex" (multi-step) tasks. My wife has difficulty performing a 3 step process on the TV remote control. She cannot follow a recipe. She cannot rmember how to make a grilled cheese sandwich. All these things involve following steps. I've written down the TV remote instructions and she sometimes cannot follow these. Writing notes or instruction may or may not help but it won't hurt to try. Executive function involves the ability to perform planning and organizational skills and is a prominent aspect of dementia.