listing the names of files

hi, I have this code that opens a file and makes it a .wk4 file
and I want it to also list the names of the files in an excel spreadsheet and put a number of how many files are listed

Sub ConvertFiles()


Dim vrtSelectedItem As Variant

Dim FileToOpen As String
'Declare a variable as a FileDialog object.
Dim fd As FileDialog
Set fd = Application.FileDialog(msoFileDialogFolderPicker)
fd.Title = "Cool Application"
fd.InitialFileName = "My Documents"
If fd.Show = -1 Then
For a = 1 To fd.SelectedItems.Count
MsgBox fd.SelectedItems(a)
Dim NextFile As String

NextFile = Dir(fd.SelectedItems(a) & "\*detail*.*")
    Workbooks.Open Filename:=NextFile
    ActiveWorkbook.SaveAs Filename:= _
        NextFile & ".wk4", _
        FileFormat:=xlWK4, Password:="", WriteResPassword:="", _
        ReadOnlyRecommended:=False, CreateBackup:=False
NextFile = Dir()

Do While NextFile <> ""
    Workbooks.Open Filename:=NextFile
    ActiveWorkbook.SaveAs Filename:= _
        NextFile & ".wk4", _
        FileFormat:=xlWK4, Password:="", WriteResPassword:="", _
        ReadOnlyRecommended:=False, CreateBackup:=False
NextFile = Dir()
Loop
Next
End If

End Sub