If you check the code of the BasicLabel, you will see that the DefaultEvent is set to no event:
<System.ComponentModel.DefaultEvent("")>
Public Class BasicLabel
Inherits System.Windows.Forms.Label
So just change it to Click event:
<System.ComponentModel.DefaultEvent("Click")>
Public Class BasicLabel
Inherits System.Windows.Forms.Label
Then the double-click should work.
Just be aware of the code that already exists for the KeypadPopUp:
'***********************************************************
'* If the label is clicked, pop up a keypad for data entry
'***********************************************************
Protected Overrides Sub OnClick(e As System.EventArgs)
MyBase.OnClick(e)
If m_PLCAddressKeypad IsNot Nothing AndAlso (String.Compare(m_PLCAddressKeypad, "") <> 0) And Enabled Then
ActivateKeypad()
End If
End Sub