Taxation under the head "Salary"

I have come across a situation where, a retrospective amemdment in the salary structure had obliged the employee to refund the allowance paid in the earlier years. The said allowances were taxed in the earlier assessment years and was repaid in current financial year 2010-11 along with interest.

In this reference, i would like to know that, is there any provision in the IT Act to deal such a situation without revising the earlier returns?

AND

Whether the amount of interest so paid would qualify for any deduction in the compuation of total income of assessment year to which it relates?

THANKS IN ADVANCE.