Here is the commented approach I have used for comparing
execution times of different pieces of code.
I have used this very approach hundreds of times over.

It is very accurate and easy to use.
In this example I am only comparing two pieces of code,
but one can use it to compare many more.

VB Code:
  1. Option Explicit
  2.  
  3. '' This function will return the total number of milliseconds
  4. ''   since the computer was started.
  5. ''
  6. Private Declare Function GetTickCount Lib "kernel32" () As Long
  7.  
  8. Private Sub Form_Load()
  9.     '' We need a variable as a counter for our loops
  10.     ''
  11.     Dim i As Long
  12.     
  13.     
  14.     '' We also need variables to store the times taken
  15.     '' In this case we're comparing two pieces of code
  16.     ''   so we'll use two variables
  17.     ''
  18.     Dim time1 As Long, time2 As Long
  19.     
  20.     
  21.     '' The basic idea here is that we record the time
  22.     ''   before we start doing the comparison,
  23.     ''   then run the code a few times,
  24.     ''   and then check the time afterwards.
  25.     '' The time taken is the time before we start
  26.     ''   subtracted from the time we finish.
  27.     ''
  28.     
  29.     '' So record the time before we start
  30.     ''
  31.     time1 = GetTickCount
  32.     
  33.     '' Now because code fragments normally execute
  34.     ''   extremely fast, in order to actually get
  35.     ''   decent times to compare, we'll have to
  36.     ''   run the code a number of times in a row
  37.     ''
  38.     For i = 0 To 100000
  39.         
  40.         '' Call the code fragment
  41.         ''
  42.         isNumberNegative1 10
  43.     Next
  44.     
  45.     '' Now subtract the time we started at from the
  46.     ''   current time
  47.     time1 = GetTickCount - time1
  48.     
  49.     
  50.     time2 = GetTickCount
  51.     For i = 0 To 100000
  52.         isNumberNegative2 10
  53.     Next
  54.     time2 = GetTickCount - time2
  55.     
  56.     MsgBox "time1 : " & time1 & vbCrLf & _
  57.             "time2 : " & time2, vbInformation
  58.     
  59. End Sub
  60.  
  61.  
  62.  
  63. '' Here are the two code fragments we'll be testing
  64. '' They will both tell whether a number is a negative
  65. ''   number of not, but what we want to know, is which
  66. ''   one is faster.
  67. ''
  68.  
  69. Private Function isNumberNegative1(ByVal num As Long) As Boolean
  70.     isNumberNegative1 = num And -1
  71. End Function
  72.  
  73. Private Function isNumberNegative2(ByVal num As Long) As Boolean
  74.     isNumberNegative2 = num < 0
  75. End Function