How to interface NX UG with VB.net

The answer depends on what you mean by "interfacing with NX". All the code on this site works with NX in some way and the vast majority is written in VB. Some of it allows user interaction in some way (e.g. selecting objects or entering values). If you want to create dialog boxes with the look and feel of NX, you will need to use the "block UI styler". If you do not have that license, you can make use of Winforms designed in your IDE of choice.
http://nxjournaling.com/content/using-winforms-journals

If you want to start a hidden session of NX and process parts with no UI, you can use the "run_journal" utility. If you search the site, there are a few examples of this.

If you want to write an application that connects to an existing NX session, you can use "remoting". There is an example that ships with NX; check your {NX install}\UGOPEN\SampleNXOpenApplications\.NET\RemotingExample folder. AFAIK, there is no remoting code on this site, but you might want to search on the Siemens "NX customization" forum:
https://community.sw.siemens.com/s/topic/0TO4O000000MiiWWAS/nx-customiza...