How to add STEP file into assembly using VB.API

Hello,

I'm trying to automate adding models to assembly.

All models that we assemble comes as step files. Our workflow now is:

1. Start new assembly 

2. Press assemble button -> Choose step file -> click Ok few times -> repeat until complete

I'm looking for a way to shorten step 2 by being able to select multiple step files, however I can't find a way in VB.API to add step files into assembly.

Extra info:

Step files comes as both assemblies and parts