Calling method with UI button.

Hello, I'm trying to get a button to continually call a method via a UI button. Mainly the "respondInput" im not sure how to use the if statement to call the movement code. I've also tried the event trigger too but does not work with how the code is written. Is there a way to do this or should I rewrite it?

Code (CSharp):

1. void Update()
2.     {
3.         if (state == State.Main)
4.         {
5.             respondInput();
6.         }
7.     }
8.  
9. public void respondInput()
10.     {
11.         if (Input.GetKey(KeyCode.X))
12.         {
13.             respond();
14.         }
15.         else
16.         {
17.             Code
18.             Code
19.         }
20.     }
21.  
22.     public void respond()
23.     {
24.         MovementCode
25.     }