Can someone help me out and explain (show an example formula) of how to use
Harlan's pull function?

It sounds exactly like what I need, but I cannot get it to work. Below is
what I have input into the cell which I need to recover data from a closed
workbook.

=pull("'"&ModelDir&"\[jointdefaults.xls]Defaults'!$C$21")

am I even close?

The spreadsheet is always named jointdefaults.xls and the folder path is
obtained in the range ModelDir.