Cells Revert Back To Letters Instead Of A Symbol

The code brings up the message box the way I need it to

At the bottom of the code in the standard module is what I changed.
In the message box. If the GDT button is clicked the GDT chart opens. If the Symbol button is clicked the Symbol chart opens. This all works.

But will I select a symbol from the symbols chart it will appear in the cell that is double clicked. but then end up as a letter instead of a symbol.

But, the gdt chart works perfect.

I thought Cancel = True Would do the trick but does not. Any ideas what is missing??

This code below is in the sheet module

Private Sub Worksheet_BeforeDoubleClicK(ByVal Target As range, Cancel As Boolean)
ThisWorkbook.Unprotect
ActiveSheet.Unprotect
With Application
Cancel = True............