Evaluating lisp expression at tab stop

[hiorig]

I was wondering if it is possible to evaluate a lisp expression at the tab stops. I'm trying to create a snippet to help me write japanese in LaTeX.
The snippet would be something like
\edtext{\ruby{$1}{$2}}{\Afootnote{$2: $3}}$0
Where I'd like to use different input-methods on each tab stop.
So something like evaluating (set-input-method 'japanese) at $1, (set-input-method 'japanese-hiragana) at $2 and (set-input-method nil) at $3.
Extra points being able to return to my original input-method before invoking the snippet