Null symbol cross platform

[David V Glasgow]

Hello, folks.

I already posted this, but no response.  I have a bit more informations and new areas of confusion, so I thought I would try again.

I have a group displaying a number of single character fields which can be clicked on to populate other fields.  Essentially a pick list.  One of the options is the null set character ( the O with a line through it, U+2205).  I have tried to find a cross platform font that displays it on Mac & Win.  I got some apparently duff info that Trebuchet would do the trick,  It is OK on Mac, but appears as the mystery character box on Win standalone.  

So I did some more digging, and it is listed among the characters displayed by unicode Arial MS.  So I set the fonts accordingly and again it works fine on Mac, but when I test a build on Windows, I get the mystery box.  This really surprised me.  I did wonder whether I might get the NUL symbol appearing as letters top left to bottom right (U+2400), but the no such character surprised me.

I have never attempted any unicode jiggery pokery - is that what I need to do, and if so, any guidance?

Best wishes,

David Glasgow