Private Sub Form_KeyPress(KeyAscii As Integer)
    ' Test for the enter key being pressed
    If KeyAscii = 13 Then
        ' cancel the keypress
        KeyAscii = 0
        ' call the tab key
        SendKeys "{TAB}"
    End If
End Sub

Private Sub Form_Load()
    ' let the form capture keyboard events
    Me.KeyPreview = True
End Sub