Organizing A Small Business

"My ADHD husband has a small outdoor advertising company. I have started to work with him and am trying to help him get the business organized so that he can keep up with his clients. He has a habit of getting distracted while on the phone, and is so often sidetracked as he works that it takes twice as long to get the job done. Of course, this makes the customers angry. Do you have any suggestions on how I might be able to help him organize his business in a consistent way that can be reviewed 'at a glance' so that he is aware of what's going on at all times?" -- CMA, TEXAS