Assign a number to signal's name : I am about to use random numbers to choose a signal but can't assign the number to that signal's name.

In this code, I have three input ports which their name are:
A1B, A2B, A3B, A4B

now I want to use them randomly by a rand function between 1 to 4.
      


    ```rand = 4, then input A4B selected.```
    ```rand = 2, then input A2B selected.```
    ```rand = 3, then input A3B selected.```


This is not an array that I use simple ().