pre-7.0.0 Unicode question

[Richmond]

I wonder why this doesn't work:

on mouseUp
    set the useUnicode to true
    if char 2 of fld "ff" is numToChar(7637) then
       set the unicodeText of char 2 of fld "ff" to numToChar(100)
    end if
end mouseUp

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AND, while I'm here:

why, when I copy from the scriptEditor do I have to paste it into 
LibreOffice,
and then recopy it to paste it into Thunderbird because it won't copy-paste
directly into my e-mail client (Thunderbird)?

Richmond.