I have Excel spreadsheet A. When I simply reference another cell in Excel
spreadsheet B (a separate file) to spreadsheet A, I don't need spreadsheet B
open to see the value in A.

However, when I include the external reference from B in any sort of a
function in A, when I have A open without B open, I get the "values" error in
A.

My hypothesis here is that one cannot use external cell references in
functions. Is this correct? Or does someone know a way around this?