reading data from field via script

Hi again,
I'm runing a script that involves importing an excel spreadsheet and then multiple pdfs, which are all joined in turn to the spreadsheet.
To eliminate error, I'd first list to read the data from a specific field in the excel file (trader ID) and from a specific field in the first pdf import (trader ID) to ensure that the matching keys are there.
The Trader ID will remain constant, i.e. it will be the same in every cell in the file.
So, for exmple,  if I could read field 4, cell 1 in file A and compare it to field 6, cell 1 in file B that would work
If I can compare the two fields at the start of the script, I can stop the script at the beginning if the user has the wrong files in the source folder.
I'm not sure if this can be done, but if it can, I'm sure you'll know how!!
All the best,
Phil