If (GetAsyncKeyState(65)) Then
Label1.Text = Label1.Text & "a"
End If

If Key A Down Then Label1.Text = Label1.Text & "a" End if
Private Sub TextBox1_KeyDown(ByVal sender As System.Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles TextBox1.KeyDown
Select Case e.KeyCode
Case Keys.A
Label1.Text = "a"
End Select
End Sub