can't drop user

Hi
I am using SQL server 2005.
I had created a login 'test12' in my database a long time back and also created a user with same name in 'infotech' database.

Now there was some requirement that i had to drop the login 'test12' so the user 'test12' became an orphaned user in my database 'infotech'

when i try to drop the user 'test12' i am getting an error as below:

Msg 15136, Level 16, State 1, Line 1
The database principal is set as the execution context of one or more procedures, functions, or event notifications and cannot be dropped.

I know i had created many functions using 'test12' in EXECUTE AS clause of my functions. so in order to drop the user i need to alter the functions in order to remove the user test12 from EXECUTE AS CLAUSE i guess.

But the thing is i have approx 200 functions from which i need to search where i had used test12 user. That is quite hectic obviously.

so is there any alternative so that i dont have to search all 200 functions???

or is there any other way to drop the user??

Thanks !!!