I finally found Entei, and with the help of a super cheater, trapped him between Mahogany and Lake of Rage.
I of course found him, had a lvl. 36 Vileplume out in front waiting to use Sleeppowder, NOW, THIS IS A MAJOR WARNING TO EVERYONE, I felt soooo stupid afterwards... I put Entei to sleep, and got him to red life I tried to use my ultra ball, and it said my box was full!!!!! So I had to let him wake up and get away, and now I can't trap him between Lake of Rage and Mahogany town anymore!!! He keeps moving and I can't catch him.
I have a Vileplume that knows Sweetscent and a Pigeot that knows Fly I believe thats all you need so could you all (PLEASE!!!) tell me how to get to him again?!