The Dallas Cowboys have three of their five seventh-round picks agreed to terms. Oregon cornerback Terrance Mitchell, the 254th overall pick, will sign a four-year deal, according to a source.He joins Stanford defensive lineman Ben Gardner and Texas Tech linebacker Will Smith as other seventh-round picks who have agreed to contracts.All three received $2.2 million deals over the four years, with minimum base salaries of $420,000 in 2014. The Cowboys, who have a $5.792 million rookie pool, have six picks left to sign.Mitchell intercepted seven passes and defensed 32 passes in his three seasons at Oregon. He will compete for a backup job behind Brandon Carr, Orlando Scandrick and Morris Claiborne.Gardner tore a pectoral muscle, limiting him to nine games last season. He had 19 tackles, 7.5 tackles for loss, 4.5 sacks and a blocked punt.Smith played at three colleges, the past two years in Lubbock. He had 120 tackles, 10.5 tackles for loss and 4.5 sacks last season.The Cowboys will likely sign more picks this week as the team's rookie minicamp gets under way Friday.Also, the Cowboys invited 15 prospects to a tryout this weekend at the minicamp.University of Louisiana Monroe's Kolton Browning will join West Texas A&M's Dustin Vaughan as quarterbacks at the minicamp. Vaughan signed as an undrafted rookie free agent earlier this week. Browning was a four-year starter with the Warhawks, passing for 10,263 yards with 81 touchdowns and 38 interceptions.The other players expected to tryout this weekend are: Robert Armstrong, Texas A&M-Kingsville wide receiver; Dartwan Bush, Texas Tech defensive end; Maurice Couch, Tennessee defensive tackle; Jyruss Edwards, Louisiana-Monroe running back; Aaron Foster, Bowling Green defensive back; Kane Friel, BYU tight end; Gus Handler, Colorado center; Josh Harris, Wake Forest running back; Lee Kurfis, Lehigh wide receiver; Eddie Lackey, Baylor linebacker; Caleb Lavey, Oklahoma State linebacker; Brandon McCladdie, The Citadel defensive back; Darius Morris, Temple offensive lineman; and Tyler Patmon, Oklahoma State cornerback.