function with single-string argument, querying sql database

Hi everyone

Please see below my codes aiming at creating a function which queries data from my database:

function x=getsqldata(var);

Set preferences with setdbprefs.
setdbprefs('DataReturnFormat', 'cellarray');
setdbprefs('NullNumberRead', 'NaN');
setdbprefs('NullStringRead', 'null');

% Set maximum time allowed for establishing a connection.
timeout=logintimeout(10);

%Make connection to database.  Note that the password has been omitted.
%Using ODBC driver.
conn = database('odbccalc', 'xx', 'xx');

% Check the database status.
ping(conn);

%Read data from database. 
var;
curs = exec(conn, ['SELECT   d.ISN ,  d.Date,  d.Px_last  FROM tblData d  WHERE d.ISN=''',var,'''']);

curs = fetch(curs);
close(curs);

%Assign data to output variable
x = curs.Data;

%Close database connection.
close(conn);

%Clear variables
clear curs conn

While running the function from the command window, I end up with:

getsqldata('CAIXUSD');
Undefined function 'Set' for input arguments of type 'char'.

Thus I wonder if someone could assist. _ In a nutshell, how to make a string variable a valid argument for this function_?

Thanks in advance

ps: the query statements works, I have tested already.

[Walter Roberson]

Which line is it reporting the error is occurring on?