VBA ListBox Form Unloading

I'm writing a audit trail that when the user changes a cell in a specified column the reason for the change gets recorded in a different sheet. If however the list box is cancelled then the cell should not change.

The code should do the following:call listbox when cell value change
user selects one or more reasons from list
if nothing selected then prompt for selection
record username, date, cell value and reasons
if click cancel then undo change, i.e. don't allow user to change the cell without selecting a reason
Steps 1-4 works well
Step5: cancel undo the cell change, but doesn't unlaod the form and hence the load-unload goes into a loop.

Private Sub Worksheet_Change(ByVal Target As Range)
If Target.Column = 15 Then
Call Launch(Target)
End If
End Sub
Module



Global reasons As String
Sub Launch(tRange As Range)
Dim prodId As String...............