Troubleshoot links - both workbooks have to be opened?
 

I have one summary workbook with links to many other workbooks. Normally,
the links return the right value, and are updated when I open the summary
workbook. Two secondary workbooks give me an #value in the linked cells of
the summary workbook until I open the secondary workbooks (no updating
required - just open & close the book). how can i prevent this requirement?