I have large numbers of cells which contain a formula as below

=IF(ISERROR(INDIRECT("'" & A2 & "'!C41")),0,INDIRECT("'" & A2 & "'!C41"))

This does exactly what it is supposed to but it definately creates a slower calculation
process when set on automatic calculation which really needs to be on. I checked using
Fastexcel and the block is creating a bottleneck. Is there another alternative to this
which would produce the same result but faster? I would welcome any guidance.

Graham