Add custom property to a listbox?
 

I know I've seen information on how to do this but now can't find it.

I have several textboxs on a userform that I want to link to a cells. I
want the textbox to have a property that points to the cell. I have the
following class:
'############## begin code ################
Option Explicit

Public WithEvents tbLength As MSForms.TextBox
Private rngSource As Range

Property Let rngSource(rngS As Range)
If Not rngS.Address = rngSource.Address Then
rngSource = rngS
tbLength.Text = rngSource.Text
End If
End Property

Property Get rngSource()
rngSource = rngSource
End Property


Private Sub tbLength_Change()
rngSource.Formula = "=" & tbLength.Text
End Sub

'############## end code ################

Now I have two issues, the first being - will this work? and the second
being, how do I add this to my control toolbox?

Any help is appreciated.

Mike