External reference to a Column
 

Hi,

I have the following formula in wb1 that only works when referenced wb is
opened:

SUMPRODUCT(--(MONTH('[P&L Fixed Income_20090414.xls]Histórico
Productos'!$A$7:$A$160)=MONTH(today)),OFFSET('[P&L Fixed
Income_20090414.xls]Histórico Productos'!$A$7:$A$160,0,M27-1)/1000)

The thing is that I want it to work when the referenced workbook is closed.
Is there an alternative solution to get the same result?

Many Thanks in Advance!!