Returning New File Names To Spread Sheet

Public Sub ListMyFiles()
Dim fso As New FileSystemObject
Dim fso_Folder As Folder
Dim fso_File As File
Dim file_count As Long

Set fso_Folder = fso.GetFolder("S:SHARED All of TransportationTraffic AssessmentMultiway Warrants")
file_count = 1
For Each fso_File In fso_Folder.Files
file_count = file_count + 1
Cells(file_count, 1).Value = fso_File.Name
Next fso_File
Set fso = Nothing
End Sub
This works great, but is there a way for the macro to recognize the file names that have already been added to the spread sheet and only return new ones that have been added to the folder?