Saw this post and took a bit of a look around the module. I have noticed parsing is not the quickest, but i have always used very small spreadsheets. I checked the Parse routine and it reads in the complete file and parses it, causing large files to take awhile to load, even if you are only going to use one cell.
The structure of the code would make it difficult to read only one cell, and the structure of the BIFF format is also working against you. If you knew the size of every cell, it would be possible to find it in the BIFF format, but a new module would be needed. Not much can be done to avoid a complete parse, and nothing i can see in Spreadsheet::ParseExcel

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may the foo be with you