This might be tricky as I assume he has been doing this for the past 6 years. You can buy special sprays from your local pet shop that discourages them to mark their territory. I own Victoria Stairwell's book "It's Me Or The Dog" and found this very helpful in the training of my dog. It should be available from Amazon online or from most good bookstores. If you are unable to get a copy I would suggest that you use a firm tone of voice when you find him toileting indoors and if you discover an accident, bring the dog to it, point at it and say no in a strict voice.You should give him plenty of encouragement and praise when he does his business outside and take him out as often as possible.
You could start by feeding him only when you get home from work, so that he he eats, and digests his food at night, thus expelling, in the pm. Start letting him out at night and walking him, seems like a lot of trouble at first, but you brag on him for going outside, you can also in combo offer him a treat along with the praise.
You can remove his food during the day, but you can never remove his water. You can never control his h20 intake (toilet, sink,ect.) It could also be fatal. Keep in mind for 42 people years he's been doing things, well, his own way. At very least this problem will require dillagence, and patience.
If you can get him going outdoors, at least better. He still might have control issues. Put him in a room, preferably with a hard floor, put down your papers, or pad, make it were he only has access to the designated area.
I disagree with above mentioned suggestion, of the stern voice treatment, because he is so old, he'll have no idea of what the problem is, why your mad, making him nervous, increasing the problem. In this case praise praise praise, when it's earned. I have heard mixed comments about the 'off' spray. Its definatly worth a try. Hey sometime let me know how it's going. Good fortune