Automatically update links in Excel doc from PowerPoint without opening Excel

[KEBE222]

Hello, I have been trying to find an answer to the following question from various sources with no luck.

I have a PowerPoint that is linked to Excel Doc A. Excel Doc A pulls information from Excel Doc B. I want Excel Doc A to automatically update from the information in Doc B without having to open Doc B.

Ideally a Macro to update Excel Doc A would run in PowerPoint each time the PowerPoint starts over, but I am open to other ideas for timing.

Thank you in advanced for your help,
Katie