Time required to read presentation - vba

Question

There are around 500 slides, the first slide is an introduction, second slide is for instructions with the action button for the Start_time macro - once clicked the timer starts. Slides 3 - 499 have one word in each, so the reader will have to go through each of the slide in a period of time, that's why the word_count equals slide.count minus three. The last slide will have the action button that when clicked will show the reading evaluation.
This macro is for my PowerPoint presentation intended to give a reading evaluation to my students.
Dim Start_time As Date
_______________________________________________________________________________________
Sub Start_time()
'at action button click in the first slide the time starts counting
Start_time = Now()
End Sub
_______________________________________________________________________________________
Sub ReadingTime()
'at action button click on the last slide the evaluaton message appears
Dim Reading_Time As String
Dim End_Time As Date
Dim iTotal_time As Long
Dim Word_count As Integer
End_Time = Now()
iTotal_time = DateDiff("d", End_Time, Start_time)
Word_count = ActivePresentation.Slides.Count - 3
Reading_Time = Word_count / iTotal_time * 24 * 60
MsgBox "Evaluation : Your reading speed is " & Reading_Time & "words per minute"
End Sub

Answer 1

Didn't you mean end_time = now()?!!!
Another deeper issue is you probably want to declare start_time at the top of the module as it will go out if scope (I.e. will no longer be available) once the start_time sub exits: type
dim start_time
right at the top of the module to do this.
Try this:
Dim m_start_time As Date 'renamed this as it clashes with a function name
Public Sub Start_time()
'at action button click in the first slide the time starts counting
m_start_time = Now()
End Sub
Public Sub ReadingTime()
'at action button click on the last slide the evaluaton message appears
Dim Reading_Time As String
Dim End_Time As Date
Dim iTotal_time As Double 'use a double as fraction days are important
Dim Word_count As Integer
End_Time = Now()
iTotal_time = End_Time - m_start_time
Word_count = ActivePresentation.Slides.Count - 3
Reading_Time = Word_count / iTotal_time * 24 * 60
MsgBox "Evaluation : Your reading speed is " & Reading_Time & "words per minute"
End Sub