Difficult to say without any formulas shown!

But it sounds a bit as if you're using VLOOKUP with the 4th argument omitted
or set to TRUE

--

Kind Regards,

Niek Otten

Microsoft MVP - Excel

"Dimitri Kryukov" <Dimitri wrote in
message ...
I am having a problem in a table that calculates P&L on each security in
the
database. It would not distinguish between different classes of security
even
though each security has a unique identifier.

For instance, it calculates SBER and SBERP as having identical P&L in a
month where only SBERP has produced P&L

In months where both securities produced P&L it calculates the results
accurately.

What am I doing wrong?