How to implement FileGlobals variables select popup with CVI?

 Good Morning!

I am developing a program in CVI 2013 using TestStand API to create some custom step types.

One of them requieres to show a window, similar to the one FileSelectPopup shows, to allow the user to select an existing variable from FileGlobals of a sequence file and the possibility to create a new one. 

I found methods GetNumSubProperties and GetNthSubPropertyName to list variables from TestStand but for this program i need to have an interface similar the FileSelectPopup function creates to select files in CVI.

Thanks in advance!

Alejandro