Possible Duplicate:
Importing a Single Symbol From a Different Font
Is there a command like \mathfont[font]{}, which enables me to use a different mathematical font for everything inside the parenthesis { } ?
I want for example to use \mathfont[txfonts]{$\mathbb{I}$}, so that just the blackboard symbol for "I" is display using the txfonts font, while the rest of my text uses the usual computer modern latex font.
I know there are similar questions and answers, but I can't get anything out of them, since to apply them, I have to know slot in the font of the symbol I'd like to import.