Pulling In Lots of Files, Create Formulas To Pull In Automatically?

I have a spreadsheet in which I'd like to pull in data from a few hundred other spreadsheets like as follows, and I have probably 150 data points in each spreadsheet:

Cell I1 =[0001.xlsx]Aggregation!$I$9
Cell I3 =[0002.xlsx]Aggregation!$I$9
Cell I5 =[0003.xlsx]Aggregation!$I$9
...
Cell I500 =[0250.xlsx]Aggregation!$I$9

with ~150 cells per row concluding in:

Cell JA1 =[0001.xlsx]Aggregation!$JA$9
Cell JA3 =[0002.xlsx]Aggregation!$JA$9
Cell JA5 =[0003.xlsx]Aggregation!$JA$9
...
Cell JA500 =[0250.xlsx]Aggregation!$JA$9


Since the files are closed normally, I can't use the INDIRECT function to assemble the formula on command (but it works for open files). I have a cell in each row in which I'm pulling data in that has a numeric value for that data (i.e. 1,2,3...250 as above).

I cannot seem to come up with a good way to get these rows of data created short of manually finding and replacing the part of the file name. Can someone help me with an idea of how to do this more quickly? Thanks!

The add-in below is what I use when I need to use the =INDIRECT function with closed workbooks.

http://www.ashishmathur.com/tag/indirect-ext/

Thanks for the thoughts! Unfortunately I have to send this workbook on to others on multiple platforms (I'm authoring it in Mac Excel anyway, but I have access to Windows Excel if needed).

Can you think of anyway to develop these formulas? We won't need to change the formulas in the future, so it's really about finding a way to increment the serial number of the filenames once across all these cells. Thanks!