Robert C. Dutton, a retired Air Force colonel who helped run a private program to aid the Nicaraguan rebels, testified before a federal grand jury investigating the Iran- contra affair after receiving a grant of immunity from independent counsel Lawrence E. Walsh, it was reported. Dutton worked with retired Air Force Maj. Gen. Richard V. Secord in supplying arms to the rebels, the New York Times reported. He had previously invoked the Fifth Amendment's guarantee against self-incrimination. Meanwhile, Sen. William S. Cohen (R-Me.), appearing on CBS' "Face the Nation," questioned presidential involvement in the solicitation of aid for the contras from foreign leaders, suggesting that a foreign donor might hope for "something in return."