Normal buttons require ALT-key to be pressed. If you don't mind this, name the buttons
Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
Button1.Text = "&1"
Button2.Text = "&2"
and trap "number"-buttons
Private Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click, Button2.Click
Select Case CType(sender, Button).Text
' Number 1 pressed
' Number 2 pressed
If you do not want ALT-key to be used, you have to trap KeyUp or similar event and use some other control instead of Button control.
I assume you have your click event sub proceedure running, to add another event for a button say "button1" you have to make sure you have enable its 'tabstop' property and then you can add another event sub proceedure.
However for your calculator, when the tabstop gets to the 'btn1' button all the user has to do is to press the "enter key".
This is in simple context, however you may have to implement threading for complex scenario where you need responses. (My opinion)
I am leaving you with some code snippet for your review, it may help.
Private Sub btn1_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles btn1.KeyPress
Dim keyasc As Short
If keyasc >= System.Windows.Forms.Keys.D1 And keyasc <= System.Windows.Forms.Keys.D9 Then
txtDisplay.Text = Val(btn1.Text)
MessageBox.Show("Error key pressed")