How to get an indoor/outdoor kittie used to being an inside kittie

Ok well as some of u may no willie has been home for about a month now and hes doing so well, hes even played which was odd, now willie is 11 years old and he was a friendly feral stray when he was taken to the shelter when he was three and of course we adopted our big fluff ball (Idk why people overlooked him so cute and fluffy and just soo friendly) But he was always indoor/outdoor he never really left our street (we are the only house on my street) and well he spent most of his time in our yard which is huge, but this time was too bad when he went missing (willie has to be so nice and follow everyone for attention) So a cat thats always been hard to keep indoors, how do we get him used to the idea of being an inside only kittie, he keeps going to our sliding glass door and we keep telling him no (see he started with my dad because its my dad and he always is the one who let him out even that night which still makes me mad becuase i always said dont let willie out at night) and well how do we ease this one to him and everything, trust me we have no intention on letting him outside no one does in this house, but i just dont know what to do, will he ever get used to the idea of being an inside only kittie (he went out maybe 2-3times a day and we be out for no longer than an hour) Any suggestions would be great, also mods if i put this in the wrong section I am sorry I just didnt know where to put it so feel free to move it to wherever it needs to go!!!! Please if any one has been through this with an older kittie or any kittie please share ur stories, any suggestions from anyone would be wonderful !!!!

i would like some answers to this one , but as i have been told by my rescue it dosnt look like its the ones we want , i have just taken in a stray whos been outside for over a yr . took him a while to trust me but we got there and got him neutered on friday. well his the most loverbale cat but always wants out , the rescue said he could be one of these cats who will live outdoors but may come in from time to time . as long as i feed him he should be fine. i would love to make him more of an indoor kitty then an outdoor . mine go out in the day time . but at night i always make sure there in. but as far as i know , it is hard to try and keep an outdoor cat indoors only. have you tried maybe a harness out in your back yard? not the collar type the one that goes round there body? least he will be able to go outside without fear of him wondering off. but being 11 might not be that easy to train. good luck hope someone else comes along with a better answer for you.