Automating InDesign CS3's GREP

Hi Folks-

I’ve managed to make a regex which replaces commas with periods, and periods with commas in some documents where numbers need to be reformatted from US>European style. I wasn’t able to do it in one go but 2 steps worked:

FIND:          (\d+)(\.)(\d+)
REPLACE:    $1,$3

FIND:          (\$)(\d{1,3})(\,)(\d{3})
REPLACE:   $1$2.$4

Inelegant, but works for our purposes.
Now, I’ve been trying to make this part of a script, but Applescript’s double-escaping has not been yielding proper results. Apple’s Technical notes helpfully suggests: “If you pass the string to display dialog or write it to a file, you’ll see it without the extra backslashes”, but I don’t want to either- I want to enter it as part of:

Tell Application "Adobe Indesign CS3"
			set find what of find grep preferences to "(\d+)(\.)(\d+)"
			set change to of change grep preferences to "$1,$3"
end tell

Double escaping yields a literal “\”. Passing a double-escape to a shell first does the same thing. Sending it to a ‘display dialog’ results in a correct single escape. Do I really need to write this to a file and then read it back?