How to remove beep when you hit "Enter" key

[Winla]

I got a couple of textbox controls for user to type in. After typing in each box, The user hits "enter" key to go next box. This is done as follow:

sub textbox1_KeyPress(KeyAscii As Integer)
   If KeyAscii = 13 Then
   sendKeys "{TAB}"
   End If
End Sub

But a beep sound comes with "enter" hit. How to avoid it? Thanks for your help