IF statement in linked cells

I have a spreadsheet that has links to 18 other workbooks, which are replaced every week. These wokrsheets are emailed in from other locations over a 7 hour time period, and I save them in a folder as they arrive.

My question is: Can I set the links so that if the linked workbook does not exist, the value in the cell is set to 0? (this way I can easily see which locations have not sent their report in, without checking the folder containing the linked files)

If I have not been clear enough in my explanation, please let me know.

Thanks in advance for any assistance,
Stuart