Hi,
I can't comment directly on the packages but perhaps your Excel Spreadsheet approach can be modified to make your life a lot easier?

Why don't you simply separate the two items? Data (your values) in one Workbook and the formulae/charts in another.

Using this approach you can happily (?) use Spreadsheet::ParseExcel to read the spreadsheet and Spreadsheet::WriteExcel to spit it back out with the new numbers... the linked spreadsheet isn't getting modified and as long as you can ensure that the filename is preserved (i.e. you don't clobber the file as someone opens the other workbook - Excel might not like that) everything should be ok.

Alternatively, store your values in a CSV format file(s) and write an Auto_Open macro in your main spreadsheet to import the values into 'named ranges' in your spreadsheet - this saves worrying about "Update Links" messages. Then you have to worry about how 'fresh' the data is.

Your approach will depend on how often the data is modified, I guess...

HTH - Mark