damn preg_replace

For whatever reason, preg_replace always kicks my ass. I've tried fifty different combos, and can't get this to work. Here's what I'm trying to do:

input string: [%1%%1099947597%]

that's 1 for user 1 and a unix timestamp.

Optimal output:

Updated by Name on 11/08/04.

Attempt:
$text = preg_replace("/[\%(.+)\%\%(.+)\%]/ie", 'Updated by $user[$1] at '.date($dateformat,'$2').": ",$text);

that doesn't work. This does:
$text = preg_replace("/[\%(.+)\%\%(.+)\%]/ie", '$user[$1]', $text);

but even adding a colon to the replacement to read '$user[$1]: ' produces a parse error.

Could someone please help?

MUCH APPRECIATED!

You're asking PHP to execute code that reads

Updated by $user[$1] at '.date($dateformat,'$2').": "

which not a valid PHP expression.

'"Updated by $user[$1] at ".date($dateformat,"$2").": "'

Weedpacket - AWESOME. Thanks for the help. Works like a charm.

Seems simple in retrospect, but those damn regexes get me everytime!