What you should get when the source file is not open is a #VALUE error
best wishes
Bernard Liengme
MVP Excel

"Fluke" wrote in message
...
Hi

I'm using Sumproduct to count rows that meet certain criteria in external
worksheets. If the other sheets are open everything is fine. If not,
then I
get the error 'Unable to read file'.

Can anyone help please? All the files are valid xls files and the path in
the sumproduct formula is fine.