Usei este código:

Dim row As Integer
row = 6

Do While (Range("A" & row).Value <> "")
    
    Dim val As String
    val = Range("A" & row).Value
    
    Dim z As Integer
    
    Dim result As String
    result = ""
    
    Dim spl() As String
    spl = Split(val, ".")
    
    If (UBound(spl) > 0) Then
        
        
        For z = 0 To Len(val)
            
            Dim r As String
            result = result & Replace(Mid(val, z + 1, 1), ".", "/")
        Next z
        
    End If
    
    If result <> "" Then
        
        Range("A" & row).NumberFormat = "@"
        Range("A" & row).Value = result
        
    End If
    
    row = row + 1
Loop

fmathias,

Bom dia!

Segue versão com correção.