This one seems to be mostly a financial question, and I have no experience with Excel's financial functions. The OP does not even seem sure of the underlying equation he should be using (though he does make reference to the ACCRINTM() function). I expect that someone who is not only familiar with Excel's financial functions but financial calculations in general (specifically interest on securities) should be able to make short work of this question.

http://www.excelforum.com/excel-gene...l-formula.html