We have created dll application for NX 10.0 using VB.NET which we run using CTRL + U but now we want custom button in Toolbar where we can execute it on click of button.
These sections in the online help should get you started:
Customizing Ribbon bar, toolbars, and menus
Create new commands
Here is a document about changes I did to edit existing NX toolbars to rename the title, remove an application and add a few more. maybe it will help.