How to add new item type validation , when trying to add new item in solution explorer of visual studio experimental instance?

Question

I am trying to add file type validation in "add-> new item" in solution explorer in visual studio experimental instance. If the selected item type is not valid, then it needs to display message box like invalid item type. Else it needs to add the selected item to the project. Currently by using this "VS.Events.ProjectItemsEvents.AfterAddProjectItems", it is adding the item before validating file type. Is there any visual studio event to call at the time of "add->new item" to validate? How to get the dialogue box of add-> new item programatically?