Calculating value stored in a string C++

[Laurio]

Im using visual c++ and I have a class which is used for calculating mathematical expressions, but im having difficulties calculating the value, because the expression is stored as a string. I need the expression in a string, because it is used in some of my other classes.
How do i calculate the value of the string?
eg
CString ExpressionStr = "2.3*sin(23)/1.7";
double Value = // value of ExpressionStr

Any help is appreciated

 

[Laurio]

problem solved, ive wrote my own parser and ps im a girl so stop calling me "he"

 

[Laurio]

Well hello......*raises eyebrow*

haha yes gents, i am a lady software engineer