Selecting Sub Folder In Folder?

I am writing a mini folder compare program to compare files in 2 folders .

I have sort of completed writing the application just that i dont know how to code for one particular part which is getting and comparing files in subfolder ( which mean my application doesnt goes into sub folder to get files name only the parent folder )

Imagine i have Folder A : with 3 files and a sub folder with 3 files

Folder B : 3 same files and a sub folder with 3 files

With the below code it only get the 3 files at the parent folder , How can i code to get the files in sub folders too ?

Private Sub chooseFirstFolder _
( _
ByVal sender As System.Object, _

[Code].....