Use INDIRECT ie:
=INDIRECT("'[BSG AGED DEBTOR ANALYSIS 2005.xls]" & A1 & "'!D11")
(assuming sheet reference in A1 of current sheet)

HTH
Cordially
Pascal

"lutts" a écrit dans le message de
...
In Excel 2002, I am referencing data from an external worksheet via the
following formula:

='[BSG AGED DEBTOR ANALYSIS 2005.xls]Jul-04'!D11

I would like to make the "Jul-04" part variable based on data entered to
the
current worksheet. If I specify, say "Aug-04", I would like to extract
data
from the "Aug-04" tab of the external worksheet, and so on..........