Sub proba()
    Dim red As Long
    For red = 2 To Cells(Rows.Count, "A").End(xlUp).Row
        If IsTime(Range("A" & red)) Then
            Cells(red, 2) = "vrijeme"
        Else
            Cells(red, 2) = "nije vrijeme"
        End If
    Next red
End Sub
Function IsTime(rng As Range) As Boolean
    Dim sValue As String
    sValue = rng.Cells(1).Text
    On Error Resume Next
    IsTime = IsDate(TimeValue(sValue))
    On Error GoTo 0
End Function