I work for an investment management firm and I am having trouble calculating
municipal bond yields with Excel.  My problem is two fold.

The first has to do with the how you write the formula or input the data.  
My traders use the following format:

yield(trade price, redemption price, rate, 2, settlement date, redemption
date, "MUNI")

If you use insert function in Excel, the format is:

yield(settlement date, redemption date, rate, trade price, redemption price,
2)

If one of my traders sends me a spreadsheet using the first format/formula,
it will properly calculate on my PC.  But if I try to edit the formula in any
way or replicate it on my own, Excel returns #NUM!  We all appear to be using
the same add-ins (I have the bond add-in installed).

The other problem is that if I use the second format, the one built into
Excel, it returns the wrong yield.  The first format of course returns the
correct yield.  How do I know it is wrong?  If I check the yield using a
financial calculator or a Bloomberg terminal it matches what the first
formula returns.

Any help would be very much appreciated!!!