how to assign a key to the scrollbar

Can someone tell me if it is possible to assign a keyboard key to use on the scrollbar to scroll up or down instead of using my mouse scroll wheel?

You should change the value of the Scrollbar using an input function. For example, to change the scrollbar via Input in the example of GUI.VerticalScrollbar, you should add this to the Update function.

void Update() {
    if (Input.GetKeyDown(KeyCode.DownArrow)) {
        vSbarValue += 1f;
    } else if (Input.GetKeyDown(KeyCode.UpArrow)) {
        vSbarValue -= 1f;
    }
}

Or with GUI.BeginScrollView as in your example:

void Update() {
    if (Input.GetKeyDown(KeyCode.DownArrow)) {
        scrollPosition.y += 1f;
    } else if (Input.GetKeyDown(KeyCode.UpArrow)) {
        scrollPosition.y -= 1f;
    }
}

thank you Veehmot, God bless you, Thank you very much