Once again, as divil said, in this code...
Dim fntFont As Font
fntFont.Bold = True
You are declaring a font object variable, then (without instantiating
it) trying to set a property. Instead, you should use one of the
overloaded Font constructors to both create the font, and set the
bold property, something like...
Dim fntFont As Font = New Font(fntOldFont, FontStyle.Bold)