Your VS Tools customizations will work just as they always have using the Dynamics GP 2013 rich client. Rich client implies the regular Dexterity written workstation installation that you use today. Using the Web Client is a different matter. The Web Client is a ground-breaking achievement for Dynamics GP and one that has long been anticipated, but it comes at a price. Any user interface that you created using WinForms will not work with the Web Client. The screen modifications you have made using Modifier work just fine, but the WinForm events will not fire when using the Web Client.
Your code will work just fine, but you need to rework your interface and register your events against a window created with Dexterity. You have two choices here. You can use Modifier and make changes to existing windows, or you can learn Dexterity and build your own windows using its graphical forms designer. You'll find the graphical forms designer feature easy to use, and making...