VBA Look Through Folder and Open Files Not Listed in Master File

So I have a master document and several hundred files with different date suffixes in the same folder. On the master document I want to list the date code and some various information in the file itself. The folder will be updated regularly so I want to be able to run the report periodically and add any new dates to the list.

So how do I do the following:

1. Search each file name in a folder
2. If the file is on my list, skip it. Else open the file.
3. Preform a function to the open file.
4. Close the file and proceed to continue checking the folder.

I cobbled together the below from various sources but it seems to have the problem of opening every file after a new file is found (eg if I have 100 files in the folder and only 97 is new, it will open file 97 to 100).

Sub ListFilesInFolder(ByVal SourceFolderName As String, ByVal IncludeSubfolders As Boolean)

    Dim FSO, SourceFolder, SubFilder, FileItem As Object
    Dim r As Long

    Set FSO = CreateObject("Scripting.FileSystemObject")
    Set SourceFolder = FSO.GetFolder(SourceFolderName)
    OrgWb = ThisWorkbook.Name
    OrgWs = ActiveSheet.Name
    Directory = "K:\Production\Robots\"
    
    r = Range("A65536").End(xlUp).Row + 1

        
        For Each FileItem In SourceFolder.Files
          FileDate = Left(Right(FileItem.Name, 12), 8)
            Set Result = Cells.Find(What:=FileDate, After:=Cells(1, 1), _
            LookIn:=xlFormulas, LookAt:=xlWhole, SearchOrder:=xlByRows, _
            SearchDirection:=xlNext, MatchCase:=False, SearchFormat:=False)
                If (Not Result Is Nothing) Then
                Else
                    FilePath = Directory & FileItem.Name
                    Workbooks(OrgWb).Worksheets(OrgWs).Cells(r, 1) = FileDate
                        Workbooks.Open (FilePath)
                        'Do Suff with Open Book
                        Workbooks.Close (FilePath)
                    r = r + 1
                End If
          X = SourceFolder.Path
        Next FileItem
        If IncludeSubfolders Then
          For Each SubFolder In SourceFolder.SubFolders
            ListFilesInFolder SubFolder.Path, True
          Next SubFolder
        
        End If
        
    Set FileItem = Nothing
    Set SourceFolder = Nothing
    Set FSO = Nothing
    
End Sub