I can't tell you how, but SageMMS does exactly this, customisation scripts
are dropped in a specific folder and read by a specific Sage DLL. Curiously,
the scripting language is VB.NET, but Sage MMS is written in C#, so the
resulting script is case-sensetive - eeww!
Each script must share the name of the module to which it applies, and
public sub main
Perhaps while giving no help at all I shown it is possible...