why do I get this error "undefined function 'left' in expression

[vicbes]

I am a new user of Access 2007.
This function worked in 2003 but will not work in 2007. The help button
displays You entered an SQL expression that includes a Function procedure
name that cannot be recognized.
However this is a valide function

 

[Arvin Meyer [MVP]]

More than likely, you have a missing reference. Here is the explanation and
solution:

http://www.accessmvp.com/DJSteele/AccessReferenceErrors.html

 

[Dirk Goldgar]

I am a new user of Access 2007.
This function worked in 2003 but will not work in 2007. The help button
displays You entered an SQL expression that includes a Function procedure
name that cannot be recognized.
However this is a valide function

Another possibility, since this is Access 2007, is that Access has disabled
all VBA code as part of its default security settings. I think that would
apply to VBA functions used in queries, too, though I can't say for sure at
the moment.

Was there a warning when you opened the database saying something about
disabling VBA? Is the database in an official "trusted location"? If not,
you might try putting it in one -- say, your Documents folder -- or else use
the Trust Center to trust the location the database is currently in.