Define code strings in shaders before compilation

Hello!
Is it possible to use different fucntions in unity shaders depending on some preprocessor macros? What I want to do is like that:

Code (CSharp):

1.  
2.     #if defined (_LIGHTMODE_UNLIT)
3.         #define SURF_FUNC surfUnlit
4.         #define LIGHTING_FUNC Unlit
5.     #else
6.         #define SURF_FUNC surfLit
7.         #define LIGHTING_FUNC Standard
8.     #endif
9.  
10.     #pragma surface SURF_FUNC LIGHTING_FUNC vertex:vert
11.  

Is this possible? By defining a keyword I can choose which function to use? (the code above doesn't work, it's for example of what I want to achieve)
Or should I do keyword definitions inside the functions themselves? (which isn't ideal, since for lit variant I just wanted to use unity default lighting)

 

Thanks for the response!