220.127.116.11 External Cell Cache
To allow external cell references to be calculated without opening the referenced workbook, an externalcellcache is stored in the file which contains cached values for cells in a sheet (1) in an external workbook (section 18.104.22.168). The externalcellcache contains cell values of the specific cells that are referenced in that sheet (1). The beginning of an externalcellcache is specified by the XCTrecord (section 2.4.352).
The externalcellcache 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 CRNrecord (section 2.4.65).