126.96.36.199 External Cell Cache
To allow external cell references to be calculated without opening the referenced workbook, an external cell cache is stored in the file which contains cached values for cells in a sheet (1) in an external workbook (section 188.8.131.52). The external cell cache contains cell values of the specific cells that are referenced in that sheet (1). The beginning of an external cell cache is specified by the XCT record (section 2.4.352).
The external cell cache is composed of a collection of sequences of cells that correspond to cells in the source sheet (1). Each cell sequence is specified by a CRN record (section 2.4.65).