I'm trying to get real-time interaction between excel and other
programs.

with automation I can send and retrieve values from/to other
applications,
but as soon as the user selects excel, the automation crashes.

Are there ways to

a) protect the excel window from crashing,
e.g. by hindering the user to get focus on it or

b) have automation and the user interfering at the same time? (would be
ideal)

thanks in advance!