INDIRECT.EXT Works for Some Spreadsheets Not Others

I installed the Excel Add-in Morefunc and it works great. The problem I have is with the INDIRECT.EXT function. On most spreadsheets it works like a charm, but on the spreadsheets that I need it to work on, it doesn't (i.e. I get a #REF! error).

Does anybody know of any reasons why it might work for some spreadsheets and not others?

Thanks in advance and happy 4th!

-Nate

I can directly link to a cell in a different work using this method:

='C:\Users\njensen\Desktop\[B393.xlsm]Recap & Subcontracts'!$H$37

or this method:

=INDIRECT(CONCATENATE("'C:\Users\njensen\Desktop\[",A1,".xlsm]Recap & Subcontracts'!$H$37"))
where,
cell "A1" = "B393"

The problem is that I don't want to open up ~75 different workbooks so that all of the values are updated correctly.

So I looked into the INDIRECT.EXT formula available through the Morefunc Add-In, and this is what I tried,

=INDIRECT.EXT("'C:\Users\njensen\Desktop\[B393.xlsm]Recap & Subcontracts'!$H$37")

Unfortunately, it did not work. I keep getting the "#REF!" error. I am, however, able to use the formula on a test excel file:

=INDIRECT.EXT("'C:\Users\njensen\Desktop\[test.xlsm]Recap & Subcontracts'!$A$1")

So here I am baffled as to why the INDIRECT.EXT function works for some workbooks and not others?

Does anybody know of a reason this might happen?

Thanks,
-Nate