Oh no question about that Donna! 
To my knowledge there aren't any tools that can/will give exact figures. But in comparison to the Moz Keyword Analysis tool (which provides BING search results), using Google Keyword Planner is about as close as you can get to an "approximate" number.
All these tools do is provide us with an idea of what to focus on. Like Rand mentioned in his post (which is great)...
"THE IMPORTANT LESSON: Running discovery-focused searches in AdWords may not show you all the valuable/high-volume keyword phrases connected to a word/phrase."
And then he goes on to recommend ways to address the challenge. FUN FUN FUN! 