Login control with web keypad

I am working on a Web POS system. One of the clients requirements is that there is no key board at the terminal.  I still need to manage users and roles.  I made a web keypad for the input with the mouse.  On page load I set focus to UserName Textbox and inputting of letters work fine with the code I am using.  I wanted to use only numbers for the password.  I used the same code but it doesn't work. I evern set focus to the Password Textbox first but still doesn't work.

Here is the code for setting focus to the UserName Textbox and what I used for the "Letter" buttons:

protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {

                Login Login1 = (Login)FindControl("Login1");
                if (Login1 != null)
                {

                    TextBox tb = (TextBox)Login1.FindControl("UserName");


                    if (tb != null)
                    {
          
                        tb.Focus();

                    }

                }

            }
        }

        

        protected void Button13_Click(object sender, EventArgs e)
        {
            Login Login1 = (Login)FindControl("Login1");
            if (Login1 != null)
            {
                TextBox tb1 = (TextBox)Login1.FindControl("UserName");

                if (tb1 != null)
                {
                    tb1.Text += "w";
                }
            }
        }

        protected void Button14_Click(object sender, EventArgs e)
        {
            Login Login1 = (Login)FindControl("Login1");
            if (Login1 != null)
            {
                TextBox tb1 = (TextBox)Login1.FindControl("UserName");

                if (tb1 != null)
                {
                    tb1.Text += "e";
                }
            }
        }

I repeated the button click events in the same manner for all the letters.

The Enter Password button sets the focus on the Password Textbox(which works fine)

I used basically the same code for the numbers but it doesn't work at all.

 protected void Button39_Click(object sender, EventArgs e)
        {
            Login Login1 = (Login)FindControl("Login1");
            if (Login1 != null)
            {

                TextBox tb2 = (TextBox)Login1.FindControl("Password");


                if (tb2 != null)
                {

                    tb2.Focus();

                }

            }
        }

        protected void Button2_Click(object sender, EventArgs e)
        {
            Login Login1 = (Login)FindControl("Login1");
            if (Login1 != null)
            {
                TextBox tb2 = (TextBox)Login1.FindControl("Password");

                if (tb2 != null)
                {
                    tb2.Text += "1";
                }
            }



        }

        protected void Button3_Click(object sender, EventArgs e)
        {
            Login Login1 = (Login)FindControl("Login1");
            if (Login1 != null)
            {
                TextBox tb2 = (TextBox)Login1.FindControl("Password");

                if (tb2 != null)
                {
                    tb2.Text += "2";
                }
            }
        }