excel concatenate text to date time stamp

I am using this code to put time stamp in cell B5:

Private Sub Worksheet_Change(ByVal Target As Range)
Dim KeyCells As Range

    ' The variable KeyCells contains the cells that will
    ' cause an alert when they are changed.

    With Me
        Set KeyCells = .Range("D5")
   
        If Not Application.Intersect(KeyCells, Target) Is Nothing Then
   
            ' we will put time stamp in cell B5
            Application.EnableEvents = False
            .Cells(5, "B").Value = Now()
            .Cells(5, "B").NumberFormat = "m/d/yyyy h:mm AM/PM"
            Application.EnableEvents = True
        End If

    End With

End Sub

It works ok however I need to concatenate  "Run at: "  to this time stamp.
Any idea.