ALTOONA, IOWA &ndash; Prairie Meadows hosts the Central Region MBNA Challenge series this weekend. The six stakes of the series are qualifiers for the 2010 Challenge Championships, to be held Nov. 20 at the Fair Grounds.\r\nBill Harris has a terrific opportunity to sweep Friday&rsquo;s Challenge races. He trains the morning-line favorite in all three Challenge races.\r\nIn the $25,110 Red Cell Distance Challenge at 870 yards, Stone E Motion looks to win his second challenge race and extend his consecutive-win streak to five. Stone E Motion had an impressive form reversal beginning with a win in a $5,000 claiming race at Hialeah Park.\r\n&ldquo;We did some vet work on his back. We were working him and he wouldn&rsquo;t really put out,&rdquo; said Harris. &ldquo;It was like a switch was thrown.&rdquo; Harris indicated that while he wasn&rsquo;t familiar with the exact procedure involved, it treated his sciatic nerve.\r\nStone E Motion will break from the rail in field of five. Lefty Ray looks to improve upon his performance in the Remington Distance Challenge. He finished fourth beaten a half a length by Stone E Motion while racing six-wide.\r\nIn the $22,500 Pfizer Starter Allowance Challenge at 350 yards, Sc Captivator heads a field of nine. Dan Boyle and Wade Siegel claimed him for $20,000 with the intention of running him in the Championship Challenge held at Delta Downs, where he finished 11th.\r\n&ldquo;We knew he just wasn&rsquo;t quite the Challenge Championship material,&rdquo; said Harris. &ldquo;We kinda got away with sneaking him into that $5,000 claimer,&rdquo; an Aug. 13 race Sc Captivator won.\r\nIn the $45,990 John Deere Juvenile Challenge at 350 yards, A Plain Brown Rapper is the field&rsquo;s fastest qualifier. A Plain Brown Wrapper takes on a competitive field of 10. Betty Jess B, winner of her trial, could improve with a slightly better break.\r\nThe $40,000 Iowa Stallion Quarter Horse Futurity at 350 yards is on the undercard. WRS Kool Jess leads a field of ten. She is coming off her maiden win at Prairie on Aug. 16.\r\nIn an earlier version of this article, William Harris was incorrectly referred to as Bill Williams.