olevba+mraptor: Detect VBA macro trigger from an Excel formula

[decalage2]

As discovered by @DissectMalware, in MS Excel a VBA macro can be automatically triggered by a formula in a cell, without requiring subs named AutoOpen and the like:
https://twitter.com/DissectMalware/status/1071566242199281664

TODO: check all cells and other places that can contain formulas, and detect if they contain the name of a VBA sub/function.