I've just used Flee to parse math functions to use for Simpson's Rule integration, just to see if I could get it to work. It turned out to be pretty simple and worked great. The code is in my comment at
One thing to watch for is that Flee is written in VisualBasic.Net. VB is case insensitive while C# isn't.
So something like IDynamicExpression eDynamic = context.CompileDynamic("sqrt(a)"), like int the flee examples fails in c# , because the method there is Math.Sqrt. Same for other Math. methods, like Cos, Abs, etc.
So remember to capitalize if you are using c#.