How can an RPM be built to trigger scriptlet before another package is updated?

Issue

There is a requirement for an RPM to have triggers whereby when one of a set of other packages are installed or upgraded the trigger will run before the packages are installed to prep the system, and then run again after the packages are installed.

%triggerin doesn't seem to work, it only seems to run after the associated package has been updated/installed.

Is it possible to trigger a scriptlet before an associated package is installed or updated?