Im not saying this is a right way for you, (and obviously depends on why your horse is going back) but its what worked for mine !

I have a 17 hand heavy horse that used this trick to object to having his feet picked up, he would run backwards and / or go up and it was getting worse on a daily basis as he soon realised that size and strength meant he was getting away with it, every time - he was starting to get really dangerous both to me and to himself

My farrier (who knew he wasnt actually doing it out of fear, but to display a show of strength) suggested 'stringing him up' which sounded awful, but just basically involved being double tied up (back through his halter) so he couldnt snap the ring (again ! you dont want to know how many lead ropes / halters I went through up till this point) and that any pressure was evenly distributed when he pulled back.The farrier then did everything he could to make Jude go back, waving arms, shouting throwing things near him etc etc and after about 10 seconds when he realised that he couldnt go back he just stood there, calm as you like, nothing we did then would even make him move !

It sounds harsh written down, but it worked a treat, it taught him that sheer strength did not get him his own way and he now stands like a dream (well like any normal horse lol)

I know that this would be the absolute wrong thing to do with some horses, but in this cas it was the right thing to stop Jude from killing me !

Have tried giving him a haynet to distract him? if that doesnt work mabe you could feed him when he is tied up then stand tied for a few seconds then untie him, and just gradually increse the time he is tied for. You dont say what breed he is but if hes an ex racer, the jockies always do it in the stable, or his pevious owner did, so hes just not used to it.