What about one of those things that screw into the ground and you attach a long line to it and to him? Give him x amout of feet to run around the yard but he'll still be tethered to the thing so he cannot get out of the yard and you won't need to watch him constantly!
Show me a pic of your boy! I have a Dexter myself!
here is a tie out
http://www.petco.com/Shop/petco_Prod...lyID_4152.aspx
and a tie out stake
http://www.petco.com/Shop/petco_Prod...lyID_9764.aspx
my boys have this and it works really well!!