Automatically updating date fields

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HI
I've inherited a set of UNIX regresion test suites (120+, slowly increrasing) held as excel spreadsheets. These sheets are ftped to Unix where a perl script converts then to various application specific functions. These spreadsheet have a lot of date fields, which need to be updated, the instructions that I have is to open/save/close all the spreadsheets before each run, which is about once a month.
Is there any way of updating the date fields in the spreadsheet without having to open/save/close each spreadsheet?
EG. a command line option, or would is need something to maybe open/save/close these spreadsheets automatically ( another spreadsheet ?)
Thanks in anticipation

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