I'm trying to run a macro on a shape to have a countdown timer but it's not working.

I want it to run on slide 3 and my selected shape is identified as 'rectangle 23', how do I reflect that on my code?

Here is the code i'm using

Sub countdown()
Dim time As Date
Dim count As Integer

time = Now()
count = 120

time = DateAdd("s", count, time)

Do Until time < Now()

With ActivePresentation.Slides(3).Shape(1).TextFrame.TextRange
.Text = Format((time - Now()), "mm:ss")

End With


End Sub