Code:

```
Private Sub Worksheet_Change(ByVal Target As Range)
If Target.Column = 4 Then
Target.Offset(, 1).Formula = "=IF(DATEDIF(RC[-1],NOW(),""y"")>0,DATEDIF(RC[-1],NOW(),""y"") & "" years"",IF(DATEDIF(RC[-1],NOW(),""m"")>0,DATEDIF(RC[-1],NOW(),""ym"") & "" months"",DATEDIF(RC[-1],NOW(),""y"")))"
End If
End Sub
```

Any help on this would be kindly appreciated.

Thanks in advance.