Great breakfast, between breakfast and lunch a meal replacement shake, then later lunch, before dinner meal replacer shake, then dinner. Thats five right there. Nothing however should ever replace good whole nutritional foods. But life aint perfect and so the meal replacers are high in protein and carbs, low in sugars(some) and is a well balanced meal. If you can do this often at work, then you could very easily sneak something else in during the day. Protein bar, apples or any fruit, a sandwich bag full of chopped up veggies to snack on. Also bring along some peanut butter in a little cup with a lid. It can stay out of the fridge all day long and you can use it to dip the fruit and veggies in, It makes for a awesome snack full of calories, good oils, protein and it gives you a nice full feeling. (do not do this with the natural peanut butter, they have to stay in the fridge)
Good luck brother!