The basic and classic and most popular mode to time your code is achieved through Timer function which is natively supplied by VBA. It returns a Single representing the number of seconds elapsed since midnight. Hence, your code will look like following when you want to measure the time and it gives the result in Seconds.
Dim StartTime As Single, TimeElapsed As Single
StartTime = Timer
< --- Your Code Follows --->
TimeElapsed = Timer - StartTime
How Accurate is Timer Function