First you need to find your RulesMD.ini file or the spawner.xdp file if you’re using the CnCnet client. I suggest opening those files with NotePad++ or some similar program. Once you’ve opened the file search for the [IQ] section and the command line RepairSell=1. Change that line to RepairSell=0 and that’s it! Start up the game and your damaged buildings will repair themselves.
If you want to add the auto repair to just one map, then all you need to do is open that map in NotePad++ and add [IQ] RepairSell=0 anywhere in the map file.
Now that you know how to auto repair in Red Alert 2 one final warning! Don’t use this change in multiplayer! It’s a cheat and I’m pretty sure the CncNet client detects the changes to the code.