How to push down a button and hold it through script?

I have two buttons, Tab and Shift. I'm using the Tab key as an accelerator.

I want to automate the "keep pressing it" part and make a shortcut to "Lock" it to being pressed down. For that, I tried using Shift.

So when I press shift ONCE, it toggles Tab being pressed down.

But I can't find a way to togle Tab though scripting.

A very important note is that I can't simply make Input.GetAxis("tab") = 1f or just copy the code I'm using on Tab to Shift, because I need to use the Gravity and Sensitivity of the button I set in the InputManager.

Here's the script

 using UnityEngine;
 using System.Collections;
 
 public class ShipThrotle : MonoBehaviour
 {
     public float speed = 100f;
 
     public float maxSpeed = 500f;
     public float acceleration = 0.01f;
 
     public float turnRate = 6005f;
     public float angularDrag = 4f;
 
     public bool isMoving = false;
 
     Rigidbody myRB;
 
 
     // Update is called once per frame
     void Update ()
     {
         myRB = GetComponent<Rigidbody> ();
 
         myRB.mass = acceleration;
         myRB.angularDrag = angularDrag;
 
 
         Vector3 vectorForce = transform.forward * speed * Time.deltaTime;
 
 
 
 
         if(Input.GetAxis ("Throtle") > 0f)
         {
             GetComponent<Rigidbody>().drag = 0f;
             GetComponent<Rigidbody>().AddForce (vectorForce);
             myRB.velocity = Vector3.ClampMagnitude (myRB.velocity, maxSpeed);
         }
         
         if(Input.GetAxis ("Throtle") < 0f)
         {
             if(myRB.velocity.magnitude > Vector3.zero.magnitude)
             {
                 GetComponent<Rigidbody>().drag = (GetComponent<Rigidbody>().drag + 0.01f) * 1.01f;
             }
         }
         //Debug.Log (myRB.velocity);
 
 
 
 
         //
         if(Input.GetButton("RotateLeft"))
         {
             myRB.AddTorque(transform.forward * turnRate * 2 * Time.deltaTime);
         }
 
         if(Input.GetButton("RotateRight"))
         {
             myRB.AddTorque(-transform.forward * turnRate * 2 * Time.deltaTime);
         }
 
 
         //Debug.Log (Input.GetButton("RotateLeft"));
         Debug.Log (myRB.velocity.magnitude + "Meters/Sec");
         //Debug.Log (((myRB.velocity.z / 1000) * 60 * 60).ToString("F2") + "Km/Hour");
 
         //Turn
         float h = Input.GetAxis ("Horizontal") * turnRate * Time.deltaTime;
         float v = Input.GetAxis ("Vertical") * turnRate * Time.deltaTime;
         
         myRB.AddTorque (transform.up * h);
         myRB.AddTorque (-transform.right * v);
 
 
         
     }
 }
 

Could anybody help me, please?