#define with if-else logic in C

I am simulating a client/server interaction according to Beej's Guide to Network Programming. At the beginning of my server.c file I am defining a port number with:

#define PORT "21124"

However, I will be creating several servers from this file and I would like to change this constant based on some if-else logic. Is there a functionality in C to easily accomplish this such as:

if (serverNumber == 1) {
  #define PORT "21124"
}
else if (serverNumber == 2) {
  #define PORT "12412"
}
else {
  #define PORT "12334"
}

This may be a duplicate, but I didn't see it in the search. I'm a C noob.