Option Explicit

Sub TestPath()
    Dim objFSO As Object
    Dim objRange As Range
    Dim i As Integer
    
    
    Set objFSO = CreateObject("Scripting.FileSystemObject")
    
    With ThisWorkbook.ActiveSheet.UsedRange.Rows
        For i = 2 To .Rows.Count
            If objFSO.FolderExists(objFSO.BuildPath(.Cells(i, 1).Value, .Cells(i, 2).Value)) Then
                Union(.Cells(i, 1), .Cells(i, 2)).Font.ColorIndex = 10
            Else
                Union(.Cells(i, 1), .Cells(i, 2)).Font.ColorIndex = 3
            End If
        Next
    End With
    
    Set objFSO = Nothing
End Sub

Предполагается, что первая строка отдана под заголовки столбцов.