How can I detect the time someone uses input?

I have a jump function that's using addforce to create the jump - There is also a double jump, that adds jumpSpeed to the first jump's velocity.y

Problem is that if the player presses the space bar really fast, the character jumps really high, because at the start of the jump velocity.y is much higher than it is a fraction of a second later

I want a jump and double jump function that works consistently - My idea is to divide the jump into seconds - if the player presses the spacebar twice within .1 seconds, then no force is added, etc etc

How can I record when the spacebar is pressed? If I know that, I can simply do (inputA - inputB) < 0.1f do nothing

Here's my jump function

 void Jump()
     {
         rigidbody.AddForce(0,jumpSpeed,0);
         jumpCount++;
         isGrounded = false;
     }

and how I call it

 if((jumpCount < 2 && Input.GetButtonDown("Jump")) && !bossArea) // ******* jump
         {
         
             if(Random.Range(0,1) == 0 && jumpCount < 2)
                 audio.PlayOneShot(jump_a);
             else
                 audio.PlayOneShot(jump_b);
         }